Itwas_____itraisedsomanydifficultquestions_____thebooktookalongtime

It was _____ it raised so many difficult questions _____ the book took a long time to come out.A.that; thatB.since; whichC.because; thatD.because; which

C解析试题分析：考查强调句：强调句的结构是：It is/was+强调部分+that+其余部分，判断是否是强调句的方法是：去掉it is/was+that…句子还能完整，就是强调句，如果把it is/was+that…去掉，这句话变成the book took a long time to come out. _____ it raised so many difficult questions句意：这本书很长时间才出版，因为它引发了很多问题。选C.考点：考查强调句型点评：强调句型在高考中每年必出，关键是要会判断，平时练习时要有这个意识。it is /was+被强调部分+that/who+…判断方法是去掉it is /was that/who句子不缺成分，即为强调句型。

就是这个解释