阅读理解。
Every year when the Italian artist Michelangelo's (1475－1564, 意大利文艺复兴时期著名雕刻家、画家、
建筑师) birthday comes around, computer users all over the world are filled with fear (害怕) and use their
computers with care. Some may even choose not to turn on their computers on March 3. All this fear and care
are just because a deadly computer virus is ready to cause damages (破坏) on that day.
What's a computer virus then? Why do people get so afraid of it?
A computer virus is, in fact, a little program that is put into other programs and that does something bad.
It is called a virus because, like any real-life viruses such as AIDs virus, it reproduces itself. And when these
programs are run, the virus is brought to life. It hides itself in your computer system waiting for the right
moment to make damages. And at the same time it keeps producing itself by copying itself onto other programs.
The Michelangelo virus waits until the artist's birthday comes around, and then it will wake up to do very
bad things like destroying you files (毁坏文档). So next time when you turn on your computer, look out for
computer viruses!
1. The Italian artist Michelangelo _____.
A. was born six centuries ago
B. was born on March 3, 1475
C. died six centuries ago
D. died on March 3, 1564
2. Why are computer users full of fear on March 3? Because _____.
A. it is the birthday of a famous Italian artist
B. a kind of computer virus will come on that day
C. a deadly computer virus called "the Michelangelo virus" will wake up and then damages that day
D. something will easily go wrong with computers
3. In fact, a computer virus is _____.
A. a program which can be put into computers with some damages to them
B. a kind of real-life virus
C. a kind of virus like AIDS virus
D. also a kind of program which is placed into other programs and which makes damages
4. In fact, a computer virus is ready to cause damages _____.
A. any day
B. only on March 3
C. on Fridays
D. only on some famous artists' birthdays
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为薄膜两侧气体的压强差。k称为该薄膜材料在该温度下对该气体的透气系数。透气系数愈小，材料的气密性能愈好。图为测定薄膜材料对空气的透气系数的一种实验装置示意图。EFGI为渗透室，U形管左管上端与渗透室相通，右管上端封闭；U形管内横截面积A=0.150cm2。实验中，首先测得薄膜的厚度d=0.66mm，再将薄膜固定于图中
处，从而把渗透室分为上下两部分，上面部分的容积
，下面部分连同U形管左管水面以上部分的总容积为V1，薄膜能够透气的面积S=1.00cm2。打开开关K1、K2与大气相通，大气的压强P1＝1.00atm，此时U形管右管中气柱长度
，
。关闭K1、K2后，打开开关K3，对渗透室上部分迅速充气至气体压强
，关闭K3并开始计时。两小时后，U形管左管中的水面高度下降了
。实验过程中，始终保持温度为
。求该薄膜材料在
时对空气的透气系数。（本实验中由于薄膜两侧的压强差在实验过程中不能保持恒定，在压强差变化不太大的情况下，可用计时开始时的压强差和计时结束时的压强差的平均值
来代替公式中的