阅读理解。
Australia is the largest island in the world. It is a little smaller than China. It is in the south of the earth.
Australia is big, but its population is small. The population of Australia is nearly as large as that of Shanghai.
Enough laws have been made to fight against pollution. The cities in Australia have got little air or water
pollution. The sky is blue and the water is clean. You can clearly see fish swimming in the rivers. Plants
grow very well.
Last month we visited Perth, the biggest city in Western Australia,and went to a wild flowers' exhibition. There we saw a large number of wild flowers we had never seen before. We had a wonderful time. Perth
is famous for its beautiful wild flowers. In spring every year Perth has the wild flowers' exhibition. After
visiting Perth, we spent a day in the countryside. We sat down and had a rest near a path at the foot of a
hill. It was quiet and we enjoyed ourselves. Suddenly we heard bells ringing at the top of the hill. What we saw made us pick up all our things and run back to the car as quickly as we could. There were about three hundred sheep coming towards us down the path.
Australia is famous for its sheep and kangaroos.After a short drive from any town,you will find yourself in the middle of white sheep. Sheep, sheep, everywhere are sheep.
1. Australia is ______.
A. the largest country in the world
B. larger than China
C. as large as Shanghai
D. not so large as China
2. Enough laws have been made to ______.
A. increase the population
B. grow more plants
C. fight against pollution
D. show wild flowers
3. Perth is ______.
A. the capital of Australia
B. in the west of Australia
C. in the east of Australia
D. the biggest city in Australia
4. In Perth you may visit the wild flowers' exhibition in ______.
A. October
B. January
C. May
D. July
5. Which of the following sentences is true?
A. All the big cities in Australia are seriously polluted.
B. Australia is famous for its sheep, kangaroos and large population.
C. We ran back to the car because we were in the middle of the white sheep.
D. If you go to the countryside in Australia, you will see a large number of white sheep.
发生衰变，沿与磁场垂直的方向释放出一个粒子后，变为一个新核， 新核与放出粒子在磁场中运动的径迹均为圆，如图所示．以下说法正确的是（ ）
衰变