阅读理解。
Air pollution comes from factories, power stations and cars. Chemicals in the smoke from power stations
cause a lot of damage (损害；毁坏). They can travel hundreds of miles in the wind before falling to the ground
in the rain. And this"chemical rain" gradually (逐渐地) destroys trees in the forests and kills fish in the lakes. In Germany, over 50% of the country's trees had been damaged by the year 1986.
Time and time again there are serious accidents that pollute the air. In 1986 there was a serious accident at
a nuclear power station in Russia. A cloud of radiation flew across the whole Europe. It is said that 125,000
people died in Russia as a result of illness caused by this accident.
In 1984 there was a serious accident at a factory in India and a cloud of dangerous gas covered the town
of Bhopal. Over 2,500 people were killed that night, and hundreds of thousands of people were injured (受伤
的). Many of the injured lost their sight.
1. Air pollution comes from _____.
A. factories
B. power stations
C. cars
D. all of the above
2. According to the passage, which sentence is right?
A. Chemicals in the smoke from power stations can't travel far in the wind.
B. "Chemical rain" is good for the trees.
C. Chemicals in the smoke from power stations are very safe.
D. "Chemical rain" is bad for our environment.
3. In Germany, how many trees had been damaged by the year 1986?
A. A quarter.
B. A half.
C. Three quarters.
D. A third.
4. What was the result of the accident that happened in Russia in 1986?
A. Over 2,500 people were killed.
B. Many people couldn't walk.
C. Many people lost their sight.
D. Compared with (同……比较) the accident in India, more people died.
5. From the sentence"Many of the injured lost their sight." we can know _____.
A. the gas covered the town of Bhopal at that time was poisonous (有毒的)
B. gradually the injured could see everything
C. many of the injured couldn't see anything any more
D. Both A and C
-t图线； 
-t图线，得出滑块加速度的大小为a＝________m/s2（保留1位小数）。
-t图线后，得出的纵坐标截距的物理含义为____________。