问题补充：
The number of teachers in our college greatly increased last term.A number of teachers in this school from the countryside.
A. was; is
B. was; are
C. were; are
D. were; is
答案：
A. was; is
(答案→)B. was; are
C. were; are
D. were; is
解析：“the number of+名词”作主语，谓语动词常用单数形式。“a number of+名词”作主语，谓语动词常用复数形式。
