问题补充：
The number of people invited fifty, but a number of them absent for different reason.
A. were; was
B. was; was
C. were; were
D. was; were
答案：
A. were; was
B. was; was
C. were; were
(答案→)D. was; were
解析：考查谓语单复数，The number of…表示…的数量，所以第一个空是单数，a number of…表示许多，所以选D
