胆汁酸合成的关键酶是（） A.3α羟化酶 B.6α羟化酶 C.5α羟化酶 D.4α羟

房地产市场实地调研方法包括()。

A.询问法

B.观察法

C.试验法

D.投射法

E.小组访谈法

Fire can help people in many ways. But can also be very harmful. Fire can heat water warm your houses, give light, and cook food. But fire can burn things too. It can burn trees, houses, animals, or people. Sometimes big fires can burn forests.

Nobody knows for sure how people began to use fire. But there are many interesting, old stories about the first time a man or woman started a fire. One story from Australia tells about a man very, very long time ago. He went up to the sun by a rope and brought fire down.

Today people know how to make a fire with matches. Children sometimes like to play with them. But matches can be very dangerous. One match can burn a piece of paper, and then it might burn a house. A small fire can become a big fire very fast.

Fires kill many people every year. So you must be careful with matches. You should also learn to put out fires. Fires need oxygen. Without oxygen they die. There is oxygen in the air. Cover a fire with water, sand, or in an emergency, with your coat or something else. This keeps the air away from a fire and kills it.

Be careful with fire, and it will help you. Be careless with fire, and it will burn you. 

小题1:Which is true?

A．We are not sure how people started to use fire.

B．It is an Australian who started a fire.

C．We know how people began to use fire.

D．Nobody knows how to make a fire.小题2:Children mustn’t play with matches because ______.

A．matches burn paper

B．it is not interesting

C．matches can be dangerous

D．they don’t know how to make a fire with matches小题3:If you are going to put out a fire, you ______.

A．must be careful with matches

B．ought to know it can be harmful

C．have to cover it with water only

D．should keep air away from it小题4:We must be careful with fire, or it ______.

A．can be

B．warms our houses

C．might burn us

D．will help us小题5:What is the main idea of the passage?

A．Fire can help people in many ways.

B．Fire can be both helpful and harmful.

C．Fire can burn things and people

D．We must be careful with matches.

为了防止飞行物与建筑物相撞的标志灯是( )。

A．值班照明

B．警卫照明

C．安全照明

D．障碍照明

“瘦金体”指谁的书法？

强碱性土壤的PH值为（）以上。