阅读理解 "Billy! It is February 25, 2099, s

命题“对任意的x∈R，x³﹣x²+1≤0”的否定是　 [ ]

A． 不存在x∈R，x³﹣x²+1≤0

B． 存在x∈R，x³﹣x²+1≤0 　

C． 存在x∈R，x³﹣x²+1＞0

D． 对任意的x∈R，x³﹣x²+1＞0

关于上颌中切牙下列哪些是正确的 （）

A.唇侧牙槽骨壁薄

B.单根弯向远中，断面呈三角形

C.先使用近远中向摇动力

D.应用旋转力效果好

E.最后沿牙根纵轴方向牵引脱位

阅读理解。

     Mary and Peter were having a picnic with some friends near a river when Mary notice an object overhead.

"Look!" she shouted to her friends. "That's a spaceship up there and it's going to land here."

     Frightened by the strange silver-colored spaceship, most of the young people got in their cars and drove

away quickly. Peter was fond of Mary and always stayed close to her. They, more curious than frightened,

watched the spaceship land and saw a door open. When nobody came out, they went to the spaceship and

entered inside. Peter followed Mary into the spaceship and did not hear the door closed behind him. The

temperature fell rapidly and the two young people lost consciousness.

     When they woke up, they were surprised to see that they were back by the river again. The spaceship had

gone. Their car was nearby.

     "What happened?" asked Mary.

     Peter scratched (抓) his head, saying slowly, "Don't ask me. Perhaps we had a dream. Did you...Did you

see a spaceship?"

     "Yes," said Mary. "And we both went into it. Then..." she looked at her wrist. "That's funny. My watch

has stopped. Oh, well, come on. It's time to go home."

     Driving about fifty meters, they found their way blocked by a thick wall made of something like glass.

They got out of the car and tried to find their way round the wall but discovered that they were inside a

circular wall. It was like a mirror and prevented them from seeing through it.

     On the other side of the wall, strange creatures walked past slowly. A few stopped to stare through the

wall and read a new notice which, translated into English, said:"New arrivals at the zoo: a pair of Earthlings

in their natural surroundings with their mobile house."

1. When the spaceship arrived, why didn't Peter drive away?[ ]

A. He did not like leaving Mary.

B. He knew that the spaceship was harmless.

C. He was too frightened to drive.

D. There was a wall blocking the road.

2. Why did Peter enter the spaceship?[ ]

A. He saw the food and was hungry.

B. Mary told him to enter it.

C. He just followed Mary.

D. He wanted to study it.

3. Peter scratched his head so we know that _____. [ ]

A. he had lost consciousness

B. he was puzzled and did not know what to say to Mary

C. he had lost his memory

D. he was still half asleep

4. What do the words "strange creatures" mean to tell us? [ ]

A. They were wild animals in a zoo.

B. They were robbers.

C. They had landed on Earth in a spaceship and lived there.

D. The young couple were on another planet.

5. Which word in the notice tells us that Mary and Peter were not on earth?[ ]

A. natural

B. surroundings

C. Earthlings

D. house

爬泳（）的配合是保持身体匀速前进的最重要条件。

A、双臂

B、双腿

C、臂和腿

D、以上均是

联炮过程中切割导爆索只能使用（）。

A、双面刀片

B、剪刀

C、单面刀片

D、电工刀