Letting a hundred flowers blossom and a hundred schools of thought contend is the policy f

One hundred online courses make fl Harvard education_________ worldwide．

A．valuable

B．allowable

C．accessible

D．knowledgeable

nd is the policy for promoting the progress of the arts and the sciences in our land.", the underlined part is_____.

A．subject complement

B．object complement

C．attribute

D．adverbial

ers are doing in Germany and some other countries.

Car makers' research and development laboratories have already proved that mixing more noise with the help of loudspeakers can reduce the unwanted noise.

Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency (频率) mix so that the highest point of one wave happens at the same time as the lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle (周期), we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems (系统) both inside and outside the cars.

Another good thing about the use of noise-killing systems is that it saves the need for a silencer; this not only reduces the weight of a car, but also makes the motor burn less fuel and work better.

Some engineers believe that the noise-killing system will be used in most cars within a few years. But the carmakers haven't decided if they will carry it into production because it would add several hundred dollars to the cost of their cars.

Which of the following gives a general idea of how the noise-killing system works？

A．By producing pressure waves going in the opposite direction.

B．By mixing high frequency sound waves with low frequency sound waves.

C．By mixing new sound waves with the noise and sending them out together.

D．By making copies of the unwanted sound waves and letting them out a little later.

听力原文： The idea of fighting a noise by making more noise sounds strange, but that's exactly what motor engineers are doing in Germany and some other countries.

Carmaker's research and development laboratories have already proved that mixing in more noise with the help of loudspeakers can reduce the unwanted noise.

Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency mix so that the highest point of one wave happens at the same time with the lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle, we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems both inside and outside the cars.

Another good thing about the use of noise-killing systems is that it saves the need for a silencer, which not only reduces the weight of a car, but also makes the motor burn less oil and work better.

Some engineers believe that the noise-killing system will be used in most cars in 1996. But the carmakers haven't decided if they will put it into production because it would add several hundred dollars to the cost of their cars.

(30)

A．By mixing high frequency sound waves with low frequency sound waves.

B．By producing pressure waves going in the opposite direction.

C．By mixing new sound waves with the noise and sending them out together.

D．By making copies of the unwanted sound waves and letting them out a little later.

ers are doing in Germany and some other countries.

Car makers' research and development laboratories have already proved that mixing more noise with the help of loudspeakers can reduce the unwanted noise.

Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency(频率) mix so that the highest point of one wave happens at the same time as the lowest point of the other wave, the result is no sound. Therefore ,by producing a perfect copy of the noise and delaying it by half a wave cycle(周期), we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems(系统)both inside and outside the cars.

Another good thing about the use of noise-killing systems is that it saves the need for a silencer; this not only reduces the weight of a car, but also makes the motor burn less fuel and work better.

Some engineers believe that the noise-killing system will be used in most cars within a few years. But the carmakers haven't decided if they will carry it into production because it would add several hundred dollars to the cost of their cars.

Which of the following gives a general idea of how the noise-killing system works？

A．By producing pressure waves going in the opposite direction.

B．By mixing high frequency sound waves with low frequency sound waves.

C．By mixing new sound waves with the noise and sending them out together.

D．By making copies of the unwanted sound waves and letting them out a little later.

To fight a noise by making more noise sounds strange, but that' s exactly what motor engi-neers are doing in Germany and some other countries．

Carmaker' s research and development laboratories have already proved that mixing more noisewith the help of loudspeakers can reduce the unwanted noise．Physicists have known about thetechnique for a long time．Sound is made up of pressure waves in the air．If two sound waves ofthe same frequency(频率) mix so that the highest point of one wave happens at the same time asthe lowest point of the other wave, the result is no sound．Therefore, by producing a perfect copyof the noise and delaying it by half a wave cycle (周期), we can kill the unwanted noise．Usingthis technique many carmakers are racing to develop noise killing systems (系统) both inside andoutside the cars．

Another good thing about the use of noise killing systems is that it saves the need for a silencer;this not only reduces the weight of a car, but also makes the motor burn less fuel and work better．

Some engineers believe that the noise killing system will be used in most cars within a fewyears．But the carmakers haven' t decided if they will carry it into production because it would addseveral hundred dollars to the cost of their cars．

Which of the following gives a general idea of how the noise killing system works？ 查看材料

A.By producing pressure waves going in the opposite direction．

B.By mixing high frequency sound waves with low frequency sound waves．

C.By mixing new sound waves with the noise and sending them out together．

D.By making copies of the unwanted sound waves and letting them out a little later．

motor engineers are doing in Germany and some other countries.

Car makers' research and development laboratories have already proved that mixing in more noise with the help of loudspeaker can reduce the unwanted noise.

Physicists have known about the technique for a long time. Sound is made up of pressure waves in tire air. If two sound waves of the same frequency mix so that the highest point of one wave happens at the same time as the lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle, we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems both inside and outside the cars.

Another good thing about the use of noise-killing systems is that it saves the need for a silencer; this not only reduces the weight of a car, but also makes the motor burn less fuel and work better.

Some engineers believe that the noise-killing system will be used in most cars within a few years. But the carmakers haven't decided if they will put it into production because it would add several hundred dollars to the cost of their cars.

Which of the following gives a general idea of how the noise-killing system works？

A．By producing pressure waves going in the opposite direction.

B．By mixing high frequency sound waves with low frequency sound waves.

C．By mixing new sound waves with the noise and sending them out together.

D．By making copies of the unwanted sound waves and letting them out a little later.

ers are doing in Germany and some other countries.

Carmaker's research and development laboratories have already proved that mixing more noise with the help of loudspeakers can reduce the unwanted noise. Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency(频率)mix so that the highest point of one wave happens at the same time as the lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle (周期), we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise killing systems (系统)both inside and outside

Another good thing about the use of noise killing systems is that it saves the need for a silencer; this not only reduces the weight of a car, but also makes the motor burn less fuel and work better.

Some engineers believe that the noise killing system will be used in most cars within a few years. But the carmakers haven't decided if they will carry it into production because it would add several hundred dollars to the cost of their cars.

Which of the following gives a general idea of how the noise killing system works？

A．By producing pressure waves going in the opposite direction.

B．By mixing high frequency sound waves with low frequency sound waves.

C．By mixing new sound waves with the noise and sending them out together.

D．By making copies of the unwanted sound waves and letting them out a little later.

D

To fight a noise by making more noise sounds strange, but that ' s exactly what motor engi-

neers are doing in Germany and some other countries.

Carmaker ' s research and development laboratories have already proved that mixing more noise

with the help of loudspeakers can reduce the unwanted noise. Physicists have known about the tech-

nique for a long time. Sound is made up of pressure waves in the air. If two sound waves' of the

same frequency(频率） mix so that the highest point of one wave happens at the same time as the'

lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of

the noise and delaying it by half a wave cycle(周期) ,we can kill the unwanted noise. Using this

technique many carmakers are racing to develop noise killing systems(系统) borh inside and outside

the cars.

Another good thing about the use of noise killing systems is that it saves the need for a silencer; this not only reduces the weight of a car, but also makes the motor bum less fuel and work better. Sorpe engineers believe that the noise killing system will be used in most cars within a few

years. But the carmakers haven' t decided if they will carry it into production because it would add several hundred dollars to the cost of their cars.

69. Which of the following gives a general idea of how the noise killing system works？

[ A]By producing pressure waves going in the opposite direction.

[ B ] By mixing high frequency sound waves with .low frequency sound waves.

[C]By mixing new sound waves with the noise and sending them out together.

[D]By making copies of the unwanted sound waves and letting them out a little later.

根据以下材料回答题

To fight a noise by making more noise sounds strange, but that' s exactly what motor engi-neers are doing in Germany and some other countries．

Carmaker' s research and development laboratories have already proved that mixing more noisewith the help of loudspeakers can reduce the unwanted noise．Physicists have known about thetechnique for a long time．Sound is made up of pressure waves in the air．If two sound waves ofthe same frequency(频率) mix so that the highest point of one wave happens at the same time asthe lowest point of the other wave, the result is no sound．Therefore, by producing a perfect copyof the noise and delaying it by half a wave cycle (周期), we can kill the unwanted noise．Usingthis technique many carmakers are racing to develop noise killing systems (系统) both inside andoutside the cars．

Another good thing about the use of noise killing systems is that it saves the need for a silencer;this not only reduces the weight of a car, but also makes the motor burn less fuel and work better．

Some engineers believe that the noise killing system will be used in most cars within a fewyears．But the carmakers haven' t decided if they will carry it into production because it would addseveral hundred dollars to the cost of their cars．

Which of the following gives a general idea of how the noise killing system works？ 查看材料

A.By producing pressure waves going in the opposite direction．

B.By mixing high frequency sound waves with low frequency sound waves．

C.By mixing new sound waves with the noise and sending them out together．

D.By making copies of the unwanted sound waves and letting them out a little later．