【题目】School violence is increasing in primary and middle schools across the country, _________causes are difficult to find sometimes.
A.which
B.where
C.what
D.whose

【答案】D
【解析】句意：校园暴力在遍及全国的中小学校都在增加，有时，很难找到它的原因。这里考察定语从句，很难找到的是“校园暴力的原因”，故用关系代词whose引导。选D。