Only 16 percent of China’s area ____ covered with forests, so ____of us should protect trees. 

 E-mail, as well as the telephone, _____an important part in daily communication. 

The number of students in our school ________about 30,000 and ________them study hard.

–What ___ the number of the students in your school?–About two thousand. A number of them_____ from England.

Most of the mistakes ____because of carelessness.