Question

The video cameras are so nice.I really don't know_______.

Answer 1

【答案】 D.which to use

I really don't know which to use我不知道选哪一个

which充当know的宾语

which既作代词,又有它本身“哪一个”的含义,所以不用what how

不定式to choose作后置定语修饰宾语which

which也能引导宾语从句,但这句不是【这句俗称简单句】,若改成宾语从句,如下：

I really don't know which video I should choose.