问题 选择题

牛奶保鲜时间因储藏温度的不同而不同,假定保鲜时间与储藏温度的关系为指数型函数y=kax,若牛奶在0℃的冰箱中,保鲜时间约为100 h,在5℃的冰箱中,保鲜时间约为80 h,那么在10℃时保鲜时间约为(  )

A.49 h

B.56 h

C.64 h

D.72 h

答案

答案:C

得k=100,a5,所以当10℃时,保鲜时间为100·a10=100·()2=64,故选C.

阅读理解

阅读理解。

       It was a fine morning. At 7:30,Carlos went to his friend's home. He knocked al the door. "Hey,Bob! Come on!"he called,Carlos waited for three minutes. Then he knocked at the door again. At last the door opened. Bob came out. It seemed that he was sleeping. He was putting his coat on and getting some books.

     "Wake up,Bob!" said Carlos,"What's the matter with you?"

      Bob opened one eye. "Well, I watched TV last night. It was very late,but it was very good film. It was about spies. I like it very much."

       "Come on!"Carlos said,"Now we are late for school. "Carlos pushed open the door and they went to school.

    "Hey,look at that!"said Carlos. 

     Bob turned and looked."Oh,wow!"said Bob.

     A wounded(受伤的)man was coming to them. Bob and Carlos saw some blood(血)on that man's coat and trousers. The man stopped when he saw the boys.

     "Help!"he said,"Help me!"

     Carlos took Bob's arm. "We had better get out of here. That man looks like trouble!"

     The boys wanted to run away. But the wounded man ran to the boys when a black car was coming.

1. Carlos and Bob were _______ .

A. policemen

B. workers

C. teachers

D. students

2. Carlos knocked at Bob's door, and Bob _______ .

A. got up at once    

B. didn't get up all the time

C. didn't get up until three minutes later    

D. went to bed again

3. Bob liked the film on TV very much because it was about ______ .

A. doctors

B. spies

C. a wounded man

D. policemen

4. "The man looks trouble!"here means _________ .

A. he doesn't look well

B. he needs some help

C. he may be a bad man

D. he wants to help us

5. The black car ________ .

A. saw Bob and Carlos

B. found some blood on the man's coat and trousers

C. ran to the boys

D. was running after the man

单项选择题