The little boy felt grateful the couch for his letting him the game.A. for; join inB. to

问题补充：

The little boy felt grateful the couch for his letting him the game.

A. for; join in

B. to; to join

C. to; join in

D. with; join

答案：

A. for; join in

B. to; to join

(答案→)C. to; join in

D. with; join

解析：考查介词和词组：句意：小男孩对教练很感激，因为他让他参加比赛。Be grateful to sb，排除AD。join in参加活动，join是参加组织，let sb do让某人做…所以选C。