As everyone knows, there are many 　16　 of transportation in the world, like bicycles, buses, ships, trains and 　17　 .

If you are in big  18　like Shanghai or Beijing, maybe you get to school   19  a subway or you have to 　20　 to school because you live in a mountain village. Here I am just trying to say something about　21　 .

Ten years　22　, bicycles were very　23　in most villages.  24　 family had one or two of bicycles. Children got to school by bicycle; 　25　 rode bicycles to go shopping. Then motorcycles (摩托车)   26  to become popular. People no longer rode bicycles because motorcycles ran   27  faster.  But now, in some countries，bicycles are highly suggested

  28  the main means of transportation. They think buses, cars and motorcycles pollute(污染) the air but bicycles   29  . So, to live a low-carbon life,   30  a bike is a good way.

Do you know why different animals or insects have their special colors? Colors are used mainly to protect themselves.
Why can’t some birds easily catch locusts（蝗虫）? It is because locusts change their colors together with the change of the colors of crops. When crops are green, locusts look green. But as autumn comes, locusts change to the same brown color as crops have. Some other insects with different colors from plants are easily found and eaten by others. So they have to hide themselves for lives in the day and appear only at night.
If you study the animal life, you’ll find the main use of coloring is to protect themselves. Bears, lions and other animals can’t be easily seen by hunters. This is because they have the colors much like the trees.
Have you ever noticed an even more strange thing? A kind of fish in the sea can send out black liquid when it faces danger. While the liquid spreads over, its enemies can’t find it. And it quickly swims away. So it has lived up to now though it is not strong at all.
【小题1】 From the article we learn that locusts 　　　　　　　　　.

In Britain, people have different attitudes(态度)to the police. Most people generally   1  them and the job they do, but some people said that the police shouldn’t    have special   2 .
What does a policeman actually do? It is not a(n)  3  job to describe. After all，a policeman has a number of jobs to do. A policeman often has to   4  traffic, either on foot in the centre of a town, or in a police car on the roads. Indeed，in Britain, he might be in the Traffic Police and spend a lot of time  5  up and down main roads. A traffic policeman has to help keep the traffic moving，stop speeding cars and help when there is a(n)  6  .
A policeman has to help keep the  7 ，too. If there is a fight, we  8  the police to come immediately. And they often have to deal with situation at great risk of their own  9 .
We want the police to solve crimes，of course，so an ordinary(普通) policeman,    10  he is not a detective，he will often have to help   11  criminals. And   12  do we call when there is an emergency—an air crash，a fire or an earthquake？Of course the police. So a policeman has to  13  to face any terrible emergency that may happen in the modern world.
The police do a  14  job，they do it so well that I support them. But I do not envy policemen. I do not think that I could   15  do the job of a policeman.