问题补充：
Li Gang, a police officer, said that little about what his son he know the moment all the media reported the traffic accident in Hebei University．
A. did do; happened
B. would do; happening
C. could do; happened
D. did did; happening
答案：
A. did do; happened
B. would do; happening
C. could do; happened
(答案→)D. did did; happening
解析：考查时态和分词，由said可以知道是一般过去时，所以是did，what his son did意思“他的儿子所做的”，分词 happening做名词the traffic accident的后置定语，名词the traffic accident和动词happen是主谓关系，所以用现在分词做后置定语
