如果系统输入的信号大多具有突变性质时,应选用()作为实验信号。 A.阶跃函数 B.斜

题型:单项选择题

问题:

如果系统输入的信号大多具有突变性质时,应选用()作为实验信号。

A.阶跃函数

B.斜坡函数

C.抛物线函数

D.脉冲函数

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题型:单项选择题

I was woken up by a strange sound. I saw something moving by my window. I was terrified and ran downstairs. I found my mom in the kitchen, getting my brother ready for school.

"Mum, did you hear anything? I, uh. I thought I saw an alien."

"Are you all right? Just a dream ! "Mum answered.

Then I went back to my room. As I walked to the window, I cried, I saw a little alien, no more than three feet tall, with big and black eyes. It tried to run between my legs and escape through the window. Although I was scared, for some reason, I squeezed (挤) my legs together in time to catch it. It took out something and hurt me. I felt a terrible sense of nothingness and fainted (晕倒). Then I woke up.

At first, I could hardly move. I wasn't sure whether it was a dream or not. I pulled myself out of the bed and walked downstairs. I saw my mum in the kitchen. She was really getting my brother ready for school, wearing her pink clothes. Then I realized it was just a dream because in my dream she was wearing her work clothes.

From then on, I always dreamt about aliens and all the dreams felt so real. At that time, I really thought maybe I had some kind of relationship with aliens. About two months later, I stopped having such dreams. Later I realized that l used to have those dreams because I always read books or watched TV programs about aliens before I fell asleep!

小题1:What did the writer first do when he saw the alien?

A.He was too scared to move.

B.He knew it was a dream and wasn't afraid.

C.He was so scared that he fainted.

D.He thought against the alien.小题2:The writer found that it was just a dream _____.

A.as soon as he woke up

B.before he went downstairs

C.when he saw his mother

D.when he was hurt by the alien小题3:Which of the following is TRUE according to the passage?

A.The writer had the dream at night.

B.The writer's mother's work clothes might not be pink.

C.The writer's mother was worried about his dream.

D.When the writer had the dream, his family were sleeping.小题4:Why did the writer use to have dreams about aliens?

A.He had some kind of relationship with aliens.

B.He was terribly ill.

C.He often did something about aliens before going to bed.

D.The dreams were all about the writer's real experiences.

题型:单项选择题

We hope Mary ______ to us as soon as she reaches London. [ ]

A. write

B. to write

C. will write

D. wirtes

题型:单项选择题

循环系统即心血管系统。

题型:单项选择题

标志着中俄两国彻底解决了所有历史遗留的边界问题的事件是

A.共同签署《中俄睦邻友好合作条约》

B.共同签署《中俄关于21世纪国际秩序的联合声明》

C.共同签署《中华人民共和国和俄罗斯联邦北京宣言》

D.双方互换《中华人民共和国和俄罗斯联邦关于中俄国界东段的补充协定》批准书

题型:单项选择题

布达拉宫保存有历代达赖的灵塔。其中()的灵塔样式与北京北海的白塔样式相仿。

A.五世达赖

B.十世达赖

C.十三世达赖

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