商品资本的职能是( )。A．生产剩余价值B．实现剩余价值C．为剩余价值生产准备条件

穿越时空，如果你回到了几千年前的商朝，下列情景可以看到的是

①人们已经懂得了选种和治虫害②一些贵族已经建立了专门的牧场

③贵族的饭桌上出现了鸡、鸭等④看到诸侯在自己的封地里巡视[ ]

A．①②③

B．①③④

C．②③④

D．①②④

阅读理解。

     Do I really need a helmet just to ride to class?

     First, ask your physics professor what can happen to a head dropped from the normal height where you

ride, say about 5 feet up, when it hits the walkway? He will tell you about the forces the head can experience

from that drop height. Bike helmets are tested in a two-meter drop, a little higher, but that five feet is all the

force you need to mess up your brain. You don't need forward speed at all, although it can make it worse.

     Then think about accidents that happen when you ride on campus. Have you had near-collisions (碰撞)

or actual collisions with pedestrians as the students change class? Do you ever hurry to get to class and take

little chances? Have you ever seen a patch of ice or sand on a campus sidewalk? We would bet that you know

more risk factors than we do.

     And what do the statistics say? There are 800 people killed on bikes, and a half million, more or less

injured, in the US every year. Nobody keeps track of how many of those were on a campus. But we do know

that you are making a major investment in yourself for a lifetime of good returns. People with head injuries

can remember how much more they were able to do mentally before the crash, and that hurts long after other

parts heal (愈合). The effects can last forever. At your age you are just beginning to realize how much

pleasure in life comes from being experienced, smart and educated. You don't want to take a chance with that.

It means a lot to you.

     Helmets are cheap at Wal-Mart or Target, and the cheap ones work fine if you fit them carefully. It really

won't mess up your hair much in a short ride. Give it a try. 

1. The aim of this text is probably______.

A. to introduce a way to protect one's head

B. to remind students to wear helmets while riding

C. to persuade students to buy more helmets at Wal-Mart

D. to warn students against bicycle riding because of danger

2. Helmets are necessary for bicycle riders on campus because _____.

A. they will meet with an accident sooner or later

B. the brain will be protected during an accident

C. their hair will not be messed up in a short ride

D. they will have to fight against the students from other classes

3. In paragraph three, the writer mainly wants to tell us that _____.

A. riding bicycles is too dangerous

B. the traffic on the campus is often out of order

C. the number of bicycles on campus should be limited

D. it is difficult to avoid accidents while riding bicycles on campus

4. The "major investment" refers to the money for _____.

A. a safer bike

B. bike accidents

C. a helmet

D. a campus insurance

5. This passage would probably appear in the part of ______ on a website.

A. Science

B. News

C. Education

D. gym

清水稀释法可使钻井液的固相含量（）。

A、增加

B、降低

C、不变

D、无法判断

发生事故时现场人员的行动原则是（）。

A.及时报告灾情

B.积极抢救

C.安全撤离

D.妥善避灾

增加广播电视新闻信息量，重点在增加（ ）

A．广播电视消息信息量

B．广播电视专题信息量

C．广播电视评论信息量

D．广播电视连续报道信息量