问题
选择题
________is often the case, the weather has turned out well as expected.
A．Which
B．When
C．What
D．As
答案
答案：D
题目分析：考查非限制性定语从句：句意：这是常有的事，天气如所预期的那样变好了。As is often the case情况经常是这样的，as引导非限制性定语从句，指代主句的内容，在定语从句中as做主语，which可以引导非限制性定语从句，但是不能让在句首，选D。