影响尘肺病发病与否的决定性因素是（）。 A.粉尘浓度 B.粉尘分散度 C.接尘时间

阅读理解。

     For many American teenagers, having a part-time job is an important part of growing up. A part-time job

can teach teenagers important skills like responsibility (责任), independence (独立),teamwork and leadership.

     Young people can expand (扩大) their social circles beyond their classmates by making friends with

co-workers. And many teenagers find that earning their own money gives them a sense of pride and freedom.

     The US Department of Labor allows teenagers to apply for jobs at the age of 14. Popular part-time jobs

include working in ice cream stores, coffee shops, and clothing stores. During the school year, teenagers may

go to work a few times a week after their classes get out, then work for longer on the weekends.

     In the summer, top jobs for teens include working at camps, swimming pools and amusement parks. These

jobs are great for young people who want to be active and have fun while making money.

      A favorite job for many teens is babysitting (临时替人看小孩), and they can start before 14 if the parents

agree. After the children are sleeping and before the parents come home, babysitters have lots of freedom. As

long as they stay in the house and make sure the kids are okay, babysitters can do their homework, enjoy a

snack, watch TV, or talk on the phone with friends.

     It can be stressful to balance school, homework, and a part-time job. Still, many American teenagers value

their work experience and the skills they gain on the job.

1. The author thinks a part-time job can teach teenagers many skills except _____.

A. responsibility

B. teamwork

C. leadership

D. organization

2. American teenagers can work when they are _____ years old by law.

A. fourteen

B. thirteen

C. twelve

D. eleven

3. Where do American teenagers like to work most in the summer?

A. At a shop.

B. In the office.

C. At a camp.

D. At a clothing store.

4. American teenagers like to babysit because they _____.

A. can start before 14

B. can make more money

C. like to play with children

D. have lots of freedom

5. We can infer that American teenagers _____ from the last paragraph.

A. enjoy working more

B. hate going to school

C. don't have much homework

D. think that skills are important

已知过点O的直线与函数y=2^x的图象交于A、B两点，点A在线段OB上，过A作y轴的平行线交函数y=4^x的图象于C点，当BC∥x轴，点A的横坐标是______．

铜和铝是日常生活和生产中重要的金属．钛（Ti）有许多神奇的性能，越来越引起人们的关注，是21世纪的重要金属之一．依据三种金属的性质和用途，判断下列说法错误的是（　　）

A．铝是地壳中含量最多的金属元素

B．将大小、厚薄相同的铜、铝、钛分别放入等质量、等浓度的稀盐酸中，观察到钛表面缓慢放出气泡，铝的放出气泡较快，而铜的无现象，由此可推测三种金属的活动性顺序为Al＞Cu＞Ti

C．钛或钛合金放到海水中数年后仍光亮如初，这说明原因是金属钛具有很强的抗腐蚀性

D．高层建筑常采用铝合金门窗而不采用铁门窗，主要原因是铝的密度小且表面易形成一层致密的氧化物薄膜

油品自燃点与燃点之间关系是（）。

A.自燃点高于燃点

B.燃点高于自燃点

C.因油品性质而定

D.不一定

牡丹皮主产于（）

A.四川、广西等省

B.安徽、广东等省

C.安徽、四川等省

D.四川、湖北等省

E.广东、广西等省