Reports showed that it was not the first time this state-owned firm ________ serious accidents．
A.has happened
B.had happened
C.has experienced
D.had experienced
网友回答
D解析解析：根据固定句型It is/was the first time that…has/had done sth．判断，排除A、C；happen为不及物动词，后不接宾语；experience（经历）为及物动词，后接宾语。故选D．