the students who took part in the training is 450.A. A number ofB. A lot ofC. Lots of D.

问题补充：

the students who took part in the training is 450.

A. A number of

B. A lot of

C. Lots of

D. The number of

答案：

A. A number of

B. A lot of

C. Lots of

(答案→)D. The number of

解析：考查主谓一致。根据后面的is说明主语是单数形式。而ABC三项是复数形式。D项the number of…指…的数量。做主语时，谓语动词用单数形式。故D正确。句意：参加训练的人的数量是450.