单选题 Without facts, we cannot form a worthwhile opinion for we need to have factual knowledge ______our thinking.

A、 which to be based on
B、 which to be base upon
C、 upon which to base
D、 to which to be based

【正确答案】 C

【答案解析】解析：句意：没有事实，我们就无法形成有价值的观点，因为我们的想法需要以事实作支撑。此处考查“介词+which引导定语从句”的用法，base on／upon表示“根据……，以……为基础”，which引导的从句修饰“factual knowledge”，正常语序为“to base our thinking upon factual knowledge”，介词upon可提前，故从句中的主谓倒装。