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 based on

C.on which to base

D.to which to be based

答案及解析： C

句意为“没有事实，我们不能形成一个有真正价值的意见，因为我们需要有确凿的知识作为我们思考的依据”。该句是...knowledge on which we should base our thinking.的省略形式。