John couldn’t take part in the activity held at the cultural center yesterday for reasons

问题补充：

John couldn’t take part in the activity held at the cultural center yesterday for reasons.

A. series of

B. all kinds

C. the number of

D. a variety of

答案：

A. series of

B. all kinds

C. the number of

(答案→)D. a variety of

解析：考查词组：句意：约翰因为各种各样的原因不能参加昨天文化中心举行的活动。a variety of

各种各样的，A应该是a series of，B应该是all kinds of，C是…的数量，选D。