Migration enables many animals to take advantage of favorable weather and abundant food supplies in areas with changing （）．

The pollution level of the earth is increasing day by day. The governments of many countries around the world are spreading this （）to encourage their citizens to control pollution.

Migrations take place on land，in water, or in the air． Some animals migrate only short （）．Other migrations cover thousands of miles or kilometers．

Besides using environmental （），many seasonal migrators probably have an inborn “calendar” that tells them when to migrate．

Old buses are major （ ） to air pollution in this city. (contribute)

From a careful study of the （ ） made by a criminal, the police can tell the height and weight of the person. (foot, print)

When the mother saw her daughter suffering, she felt a sense of（ ）. (helpless)

Numerous animals migrate to breeding areas so that their young have the best chance for （）．

What may seem helpful advice to you can be interpreted as （ ） by others. (interfere)

He is measuring the （ ） of his dining room. (long)

Experiments show that changes in day length （）the migrations of many species of birds．

Some people believe that smoking may （）one’s life. Not only cancer, but also heart and lung diseases are related with smoking.

The government has worked out a ten-year program to （ ） the transport system of the country. (modern)

Humans, like other animals, （）with each other through communicative behavior by means of signs or symbols.

It is no use （ ） over the mistakes you have made. (cry)

So many people exhaust their health gaining wealth, and then have to spend their wealth to （ ） their health. (gain)

Humans, like other animals, （ ）with each other through communicative behavior by means of signs or symbols. (act)

Some people believe that smoking may （ ） one’s life. Not only cancer, but also heart and lung diseases are related with smoking. (short)

A number of them （）dangerous organic compounds which are unsafe for both human beings and the natural resources. 

So many people exhaust their health gaining wealth, and then have to spend their wealth to（）their health.