【题目】The number of smokers, _____ is reported, has dropped by 17 percent in just one year.
A.it
B.which
C.what
D.as

【答案】D
【解析】句意：据报道，吸烟者人数仅（过去）一年就减少了17%。as引导的非限制性定语从句位置灵活，可以置于主句的句首、句中或句末，指代的是整个一句话。故选D项。