The number of people invited fifty but a number of them absent(缺席) for different reason

问题补充：

The number of people invited fifty, but a number of them absent(缺席) for different reasons.

A. were; was

B. was; was

C. was; were

D. were; were

答案：

A. were; was

B. was; was

(答案→)C. was; were

D. were; were

解析：句意：受到邀请的人数是五十，但是很多人因为各种各样的原因而缺席。The number of表示“的数量”，其主语为数目，所以后面的谓语动词用单数形式，而a number of them表示“大量，许多”，后面修饰可数名词的复数，后面的谓语动词也用复数形式；故选C。