No sooner the petition an unexpected accident happened.
A. did … begin; than
B. had … begun; when
C. did … begin; when
D. had … begun; than
网友回答
A. did … begin; than
B. had … begun; when
C. did … begin; when
(答案→)D. had … begun; than
解析：考查倒装结构与固定句式。 No sooner...than是固定短语，而且no sooner后要用过去完成时态，放在句首要部分倒装，所以要把had提前，后面搭配than所以选D.
句意：竞赛一开始意外事故就发生了。