问题补充：
his homework, my son went downstairs to play basketball.
A. Having finished
B. finished
C. to finish
D. finishing
答案：
(答案→)A. Having finished
B. finished
C. to finish
D. finishing
解析： 考查非谓语动词作状语。my son与finish之间是主动关系，且分词的动作发生在谓语动词之前，故用现在分词的完成式，所以选A，句意：我的儿子完成作业之后他就去楼下打篮球。
