单选题 He kept his head at that critical moment; otherwise the accident ______.
A. would happen B. happened
C. would have been happened D. would have happened

【正确答案】 D
【答案解析】此题考查虚拟语气的用法。解题关键为otherwise，其暗含与前面相反的条件，因题干的时态为过去式，因此应选用D项，表示与过去事实相反的假设。