The theory he had stuck _______ to be true.
A. proved B. to proving C. to prove D. to proved
The theory he had stuck _______ to be true.
A. proved B. to proving C. to prove D. to proved
D
一看这四个选项认为是不定式后接动词原形，其实he had stuck to是充当后置定语，stick to(坚持)为一个固定搭配，去掉这个定语从句后，我们可以很清楚地发现整个句子缺少了谓语动词，定语从句时态为过去完成时，所以主句谓语动词应该过去式。