单选题 ______ that you were out, I wouldn't have bothered to come all the way at that time of night.
A. If I should know B. If I know
C. Had I known D. Were I to know

【正确答案】 C
【答案解析】[解析] 根据句意,此处应使用虚拟语气,因此,B项错误。A项尽管使用了虚拟语气,但它表示的是对一般将来情况的虚拟,所以时态不正确。为了表示语气上的强调,在虚拟条件句中可以省略if,而此时从句应使用倒装结构。例如:Had he taken a little more time to think,he might have acted more reasonably. 如果他再多用一点时间思考一下,他的行动就可能会更理智些。尽管D项也使用了倒装结构,但它表示的是对一般将来情况的虚拟,时态不正确。可见只有C项正确。