单选题 It is very necessary to know the extent ______ supply and demand will influence the price.
A. in which B. from which C. to which D. for which

【正确答案】 C

【答案解析】本题主要考查定语从句关系代词前的介词的选择，应根据前面的先行词，先行词为the extent，意为“在……程度上”是to...extent，所以C选项是正确选项。
译文：了解供需在何种程度上影响着价格是非常必要的。