In general, a third-order system can be approximated by a second-order system’s dominant roots if the real part of the dominant roots is less than 1/10 of the real part of the third root.

In general, American food is mild tasting; most Americans do not season their food to any great degree. Salads are very popular and are served all year, especially in the summer. Waiters tend to assume that everyone drinks coffee, but simply tell them if you want something else. If a waiter says "Now or later?" he means "Do you want coffee with your meal or after it?" Many, but certainly not all, Americans drink coffee or tea with their meals. Either way is perfectly acceptable. When dining out, you can ask for tea, milk, "coke", wine or beer if you prefer. Restaurants can only serve beer, wine or other alcoholic drinks if they have a license, that is, permission from the local government to serve alcoholic drinks. Normally, when eating in a private home, it is considered good manners to take whatever is served and not to ask for something different, unless the hostess gives you a choice.

The main course served in American meals is usually meat, fish, or poultry, but rarely is more than one of these served as a first course, however.

Most Americans eat breakfast and lunch quickly unless it is social, business, or family occasion. The evening meal, however, is usually longer and a time for the family to gather together. Rushing through day-time meals is part of the fast pace in America. Another reason for rushing through day-time meals is that many people who eat breakfast and lunch in restaurants are usually crowded with people waiting for a place so that they, too, can be served and return to work at the proper time. So each one hurries to make room for the next person. As with busy people everywhere there is a real difference between a meal that is eaten in a hurry and one that can be enjoyed with friends during one's leisure.

In America, salads are very popular and are served especially ______.

A．all year

B．in the summer

C．at lunch

D．at dinner

听力原文： In general, American food is mild tasting; most Americans do not season their food to any great degree. Salads are very popular and are served all year, but especially in the summer. Waiters tend to assume that everyone drinks coffee, but simply tell them if you wish something else. If a waiter says "Now or later?" he means "Do you want coffee with your meal or after it?" Many, but certainly not all, Americans drink coffee or tea with their meals. Either way is perfectly acceptable. When dining out, you can ask for tea, milk, "coke", wine or beer if you prefer. Restaurants can only serve beer, wine, or other alcoholic drinks if they have a license, that is, permission from the local government to serve alcoholic drinks. Normally, when eating in a private home, it is considered better manners to take whatever is being served and not to ask for something different, unless the hostess gives you a choice.

The main course served in American meals is usually meat, fish, or poultry, but rarely is more than one of these served at the same meal. Seafood is sometimes served as a first course, however.

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A．Seasoned foods.

B．Salads.

C．Sea fish.

D．Sweets.

If there is no difference in general intelligence between boys and girls, what can explain girls' lack of success in science and mathematics?

It seems to be that their treatment at school is a direct cause. Mathematics and science are seen as mainly male subjects, and therefore, as girls become teenagers, they are less likely to take them up. Interestingly, both boys and girls tend to regard the "male" subjects as more difficult. Yet it has been suggested that girls avoid mathematics courses, not because they are difficult, but for social reasons. Girls do not want to be in open competition with boys, nor do they want to do better than boys because they are afraid to appear less ladylike and attractive.

However, if we examine the performance of boys and girls who have undertaken mathematics courses, there are still more high-achieving boys than there are girls. This difference appears to be worldwide. Biological explanations have been offered for this but there are other explanations too.

Perhaps the difference which comes out during the teenage years has its roots in much earlier experiences. From their first days in nursery school, males are encouraged to work on their own and to complete tasks: this is essential behavior. for learning how to solve problems later on. Evidence shows that exceptional mathematicians and scientists have not had teachers who supplied answers.

Apart from that, there can be little doubt that teachers of mathematics and science expect their male students to do better at these subjects than their female students. They even appear to encourage the difference between the sexes, not consciously, but they still do it. Such male-oriented teaching is not likely to encourage girls to take many mathematics and science courses, nor is it likely to support girls who do. It seems certain, then, that where these subjects are concerned, school widens the difference between boys and girls.

Why do teenage girls avoid mathematics courses?

A．They think mathematics is not interesting.

B．They think mathematics is difficult.

C．They think mathematics is competitive.

D．They think boys will not like it either.

What is the best way to break up a boring moment and tension in the office? How does one develop one's sense of humor?

As people are fed up with lots of things in the workplace, it's healthy to create those humorous feelings. In fact, many companies now have humor rooms. In a dull moment, you may tell a funny story about something that you did. In general, real events are funnier than invented jokes. You may also show your boss or coworkers some business articles about humor—The Wall Street Journal and other publications have several such stories. Anything that makes you laugh—in print or on tape. But don't just be a consumer of humor—be a producer, too.

Start with humor and some funny stories that happened to you. The most important thing at work is to find someone who appreciates your humor. When you can laugh, somehow things don't feel so hopeless. The best humor accepts the unexpected side of things. Creativity is also strongly linked to humor. One of the exercises is to list 25 improvements for the standard. It's amazing how quickly people start to laugh as they think creatively and go for the unexpected. For example, "How about glass walls with huge fish behind them? "

Management studies show that people with a good sense of humor are more likely to have raises and go further in companies than humorless people. Actually, humor is especially useful as a social lubricant (润滑剂) —in criticisms, complaints, etc. Humor reduces the threat and tension in any situation. Please put more humors in your work.

Many companies provide______and keep magazines with funny stories to help remove the tension of their employees.

听力原文： As any homemaker who has tried to keep order at the dinner table knows, there is far more to a family meal than food. Sociologist Michael Lewis has been studying 50 families to find out just how much more.

Lewis and his co-workers carried out their study by videotaping the families while they ate ordinary meals in their own homes. They found that parents with small families talk actively with each other and their children. But as the number of children gets larger, conversation gives way to the parents' efforts to control the loud noise they make. That can have an important effect on the children. "In general, the more question asking the parents do, the higher the children's IQ scores," Lewis says. "And the more children there are, the less question-asking there is."

The study also provides an explanation for why middle children often seem to have a harder time in life than their brothers and sisters. Lewis found that in families with three or four children, dinner conversation is likely to center on 'the oldest child, who has the most to talk about, and the youngest, who needs the most attention.

"Middle children are invisible," says Lewis. "When you see someone get up from the table and walk around during dinner, it's often the case that it's middle child." There is, however, one thing that stops all conversation and prevents anyone from having attention: "When the TV is on," Lewis says, "dinner is a non-event."

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A．To report on the findings of a study.

B．To give information about family problems.

C．To show the relationship between parents and children.

D．To teach parents ways to keep order at the dinner table.