The number of people invited fifty, but a number of them absent for different reasons.
A. was, was
B. were, were
Cwere, was
D. was, were
网友回答
A. was, was
B. were, were
C. were, was
(答案→)D. was, were
解析：考查：The number of +复数名词作主语，……的数量，谓语动词用单数；a number of+复数名词作主语，许多，谓语动词用复数形式。所以选D。