______ is often the case with a new idea, much preliminary activ

______ is often the case with a new idea, much preliminary activity and optimistic discussion produce no concrete proposals.
A、That
B、It
C、Which
D、As
【正确答案】：D
【题目解析】：前半句不能是一个完整的句子，所以排除A和B，as作为物主代词可以放句首，which只能作为具体指代。