问题 问答题

A.条件(1)充分,但条件(2)不充分.
B.条件(2)充分,但条件(1)不充分.
C.条件(1)和(2)单独都不充分,但条件(1)和条件(2)联合起来充分.
D.条件(1)充分,条件(2)也充分.
E.条件(1)和(2)单独都不充分,条件(1)和条件(2)联合起来也不充分.

某列火车的平均速度是216 km/h.
(1)该列火车通过一根电线杆用了5 s;
(2)该列火车通过一个长为600 m的隧道用了15 s.

答案

参考答案:(C).

解析: 问题中含有两个未知量,一个是火车车身长,一个是火车速度,条件(1)、条件(2)各含有一个关系,因而条件(1)、条件(2)单独都不充分.联合条件(1)、条件(2)考虑,设火车车身长为l m,速度为v m/s,由条件(1)可知l=5v,由条件(2)有
600+l=15v,
600+5v=15u,
故选(C).

阅读理解

阅读理解。

     Overcoming(克服) shyness is not impossible. The following steps may be helpful.

Step 1

     Overcoming shyness is mainly a case of mind over matter. If you're afraid to do it, you will get much shyer when

doing it. The more you come to talk with people, the easier it will become. You may also find that it's not as difficult

as you thought anyway. Just talk to people a little more every day.

Step 2

     It sometimes helps to try to imagine you as another person. Think about this: Do you get shy when someone else

walks up to talk to   another? Of course you don't.   Think of   yourself as just somebody else and it'll  make it a little

easier.

Step 3

     Dress to impress. The better you look, the more confident you'll feel. Feeling good about your appearance can

greatly reduce shyness.

Step 4

     If you're up on stage, try to imagine that you're somewhere else. Maybe in your own comfortable living room. Tell

yourself that the audiences are really no big deal. They're ONLY people.

1. The first step mainly tells us   .

A. we should talk to people as much as possible

B. it's difficult to get over shyness

C. we'll be shy when talking to more people

D. we are shy because we don't think carefully

2. The second step tells us it's    to think of yourself as another person.

A. unnecessary            

B. interesting

C. useful                  

D. difficult

3. What does the underlined word "reduce" mean in this passage?

A. 喜欢      

B. 减少    

C. 增大    

D. 防治

4. We can learn from the fourth step that   .

A. it's easy to speak in our living room

B. it's easy to speak to only people

C. what to think of when speaking on stage

D. when you can speak on stage

5. What's the best title of this passage?

A. How to get over shyness

B. How to speak in public

C. Don't look on you as yourself

D. How to feel good about yourself

单项选择题