Things,-----is often the case,will turn out to be contrary t

1.答案：A.
2.翻译：正如事实的通常情况那样,事情总是和人的愿望是相反的（即“事与愿违”）.
3.
1）此题考查的非限制性定语从句的关系代词的用法.
2）关系代词as,等于并代替整个主句Things will turn out to be contrary to one's wishes这句话,在定语从句 ___ is often the case中充当主语.
3）即完整的定语从句结构为：
As is often the case.
= (That things will turn out to be contrary to one's wishes) is often the case.
此时as所代替的句子things will turn out to be contrary to one's wishes,相当于这个定语从句的主语(从句).
定语从句可以翻译为：事与愿违（这种情况）通常都是事实.