问题 单项选择题

PRS700系统(+24V),其输入输出电压范围描述正确的是()

A、输入电压范围:单相187Vac~242Vac;输出电压:22Vdc~30Vdc之间设定

B、输入电压范围:单相110Vac~310Vac;输出电压:19Vdc~29Vdc之间设定

C、输入电压范围:单相187Vac~242Vac;输出电压:19Vdc~29Vdc之间设定

D、输入电压范围:单相110Vac~310Vac;输出电压:22Vdc~30Vdc之间设定

答案

参考答案:D

选择题
阅读理解

阅读理解。

     I love science and science fiction. Like many science fiction fans, I am fascinated by the

possibility of time travel. However, one must combine romance with reasoning and look into

the chances of time travel critically.

     First of all, we must remember the whole universe is in motion. If we want to go back

to yesterday, our "time machine" has to move back in time and space. If someone claimed

he was at home when he suddenly travelled 200 years back in time, he either had an illusion

or made the story up. Two hundred years ago, Earth was in a different place in space, so

how can you travel back 200 years without moving in space? Don't get me wrong. I am not

knocking the genius of science fiction writers. H.G. Wells's "The Time Machine" is a great

work of fiction, but that's all. I have read many other time travelling science fiction stories

since reading H.G. Wells, but none address this problem of displacement.

     My own argument for the impossibility of time travel is that physical states of the past no

longer exist and those of the future are not here yet. To be able to move back and forth in

time requires everything that has happened, is happening, and will happen everywhere in the

whole universe at every single moment in time-past, present, and future-to be stored as

a "reality" somewhere-like the save game file of a computer game that contains every single

byte of information of the game at the point it was saved, but you would need an almost

extremely large file and almost extremely many of them-so it can be re-entered and

communicated with, and not just light signals for viewing. To me, I don't buy it.

1. Which of the following can be the best title?

A. How to make time travel possible?

B. Why am I fascinated by time travel?

C. Why do I think time travel is not possible?

D. How to explain the possibility of time travel?

2. What's the meaning of the underlined word "illusion"?

A. success

B. dream

C. switch

D. support

3. According to the author, which of the following is RIGHT?

A. We can go back to the past by time travel.

B. People can travel to the future by moving in space.

C. "The Time Machine" is nothing more than a science fiction.

D. Everything that happened, is happening and will happen can be stored somewhere.

4. In the author's opinion, time travel might be possible if .

A. people could combine romance with reasoning

B. people could stop the movement of the whole universe

C. people could use time machine under the instruction of H.G. Wells

D. people could "save" everything in the past, present and future in a certain space