问题 填空题

已知两个平面垂直,给出下列一些说法:

①一个平面内的一条直线必垂直于另一个平面内的任意一条直线;

②一个平面内的一条直线必垂直于另一个平面内的无数条直线;

③一个平面内的任意一条直线必垂直于另一个平面;

④在一个平面内过该平面内的任意一点作交线的垂线,则此垂线必垂直于另一个平面.

其中正确的说法的序号依次是______.

答案

①“一个平面内的一条直线必垂直于另一个平面内的任意一条直线”的说法是错误的,当一个平面内的一条直线平行于两个平面的交线时就不满足上述条件.

②“一个平面内的一条直线必垂直于另一个平面内的无数条直线”的说法是正确的,由判定定理可以推出.

③“一个平面内的任意一条直线必垂直于另一个平面”的说法是错误的,在其中一个平面内可以找到一条直线平行于另一个平面,如与交线平行的直线即可.

④“在一个平面内过该平面内的任意一点作交线的垂线,则此垂线必垂直于另一个平面”的说法是正确的,可以根据线面垂直的判定定理证明.

故选②④.

阅读理解

阅读理解。

     It's not easy being a teenager (13至19岁青少年)-nor is it easy being the parent of a teenager. You can

make your child feel angry, hurt, or misunderstood by what you say without realizing it yourself. It is important

to give your child the space he needs to grow while gently letting him know that you you'll still be there for

him when he needs you.

     Expect a lot from your child, just not everything. Except for health and safety problems, such as drug use

or careless driving; consider everything else open to discussion. If your child is unwilling to discuss something,

don't insist he tell you what's on his mind. The more you insist, the more likely that he'll clam up. Instead, let

him attempt to solve (解决) things by himself. At the same time, remind him that you're always there for him

should he seek advice or help. Show respect for your teenager's privacy (隐私). Never read him his mail or

listen in on personal conversions.

     Teach your teenager that the family phone is for the whole family. If your child talks on the family's

telephone for too long, tell him he can talk for15 minutes, but then he must stay off the phone for at least an

equal period of time. This not only frees up the line so that other family members can make and receive calls,

but teaches your teenager moderation (节制). Or if you are open to the idea, allow your teenager his own

phone that he pays for with his own pocket money or a part-time job

1. The main purpose of the text is to tell parents _____.

A. how to get along with a teenager

B. how to respect a teenager

C. how to understand a teenager

D. how to help a teenager grow up

2. What does the phrase "clam up" in Paragraph 2 probably mean?

A. become excited

B. show respect

C. refuse to talk

D. seek help

3. The last paragraph is about how to teach a teenager _____.

A. to use the phone in a sensible way

B. to pay for his own telephone

C. to share the phone quickly

D. to answer the phone quickly

4. What should parents do in raising a teenager according to the text?

A. Nor allow him to learn driving or take drugs

B. Give him advice only when necessary

C. Let him have his own telephone

D. Not talk about personal things with him

名词解释