Task 1
Directions: After reading the following passage, you will find 5 questions or unfinished statements, numbered 36 through 40. For each question or statement there are 4 choices marked A, B, C, and D. You should make the correct choice.
To preserve food, the growth of bacteria (细菌) must be controlled. Water, warmth, and food are all needed for bacteria to become strong and healthy. Some kinds of bacteria need air, but other kinds grow only when air is absent. Extremes of temperature, either hot or cold, can kill bacteria.
Before electric ice boxes were invented, freezing and cooling were limited by the cold climate. In warmer regions, food was cooled by putting it in the shade, in cold water from the well, or in pits in the ground.
Cooking will usually kill bacteria if the temperature is high enough and long enough. Certain methods of cooking remove water, and this aids in preserving food. Drying is the oldest and most common method of preserving food. Food can be dried by the sun, by heat or by combination of the two.
Salt was used by many hunting people. When people began to cat vegetables, salt be came a needed part of their life. Salt helps to preserve food because it slows or stops bacteria growth. Other chemicals besides salt are used in preserving foot. Some people oppose the use of chemicals in food. They say that these chemicals may harm people if the chemicals can harm bacteria.
Cooking is an effective way in preserving foods because .
A.cooking always kills the bacteria in food
B.cooking can make the food become dry
C.the light in cooking can kill bacteria
D.under the right conditions, cooking will kill bacteria
第3题
在有线电视系统中,以下()不是常用功分器
A.2功分器
B.3功分器
C.4功公器
D.10功公器
第4题
A.功分器输入输出倒过来用就是合路器
B.合路器各端口频率不同,功分器各端口频率相同
C.功分器与合路器隔离度相同
D.合路器可以取代功分器
第6题
A.功分器:功率分配器,将一个端口的信号功率等分给输出端口
B.合路器:功率合成,将两路或多路信号相加到一个端口
C.耦合器:将信号按照比例耦合到耦合端口
D.功分器反过来用,就是合路器。耦合器可以认为是功分器的一种,只不过不是等分
第8题
A.将机架顶两条馈线直接接入各支路的功分器
B. 用电桥合路再分别接入各支路的功分器
C. 用功分器合路再用功分器分路后接入支路的功分器
D. 机架顶一端接假负载,另一端接功分器
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