I who () your best friend will do as far as I can to help you.

问题描述:

I who () your best friend will do as far as I can to help you.
A. if B.are C.was D.were

C
个人觉得还是填am为何?从后面的will(表示一般将来时)来看,前面要用一般现在时态,这里的be动词应该和先行词I 相一致,所以用am。