A number of students trees every year and the number of them increasing.A. plant; isB. pla

问题补充：

A number of students trees every year and the number of them increasing.

A. plant; is

B. plants; is

C. planting; is

D. planting; are

答案：

(答案→)A. plant; is

B. plants; is

C. planting; is

D. planting; are

解析：本题考查number of的用法。a number of为量词短语，表示“许多……”，中心词是这个短语所修饰的复数名词，所以作主语时，谓语动词用复数形式。the number of表示“……的数量”，后接复数名词，其中，中心词为number，因此谓语动词用单数。