大全531新问

531.New techniques in thermal-scanning photography, a process that records radiation from surface areas, makes it possible to study the effects of calefaction, or warming, of a river in greater detail than ever before.
(A) makes it possible to study the effects of calefaction, or warming, of a river in greater detail than ever before
(B) make it possible to study, in greater detail, the effects of calefaction, or warming, of a river than ever before
(C) have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river
(D) make possible the study of the effects of calefaction, or warming, of a river in greater detail than it ever was before
(E) has made it more possible than ever before to study in greater detail the effects of calefaction, or warming, of a river

Key is C .      have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river

答案是C没有问题.我不太明白made后面的it做什么成分,指代什么?

it = to study in greater detail than ever before the effects of calefaction, or warming, of a viver.

to study in greater detail than ever before the effects of calefaction, or warming, of a viver  太长, 后置, 用 it 指代

你说的有道理，偶觉得还是那句话，选最好的，如果C也用一般现在时，那你的上一个题可能就做错了。

偶的理解是：AE主谓和时态不一致，不用理它们。你说的主要是BD和C的区别，D中的IT前面单数名词太多，明显的指不清，一票否决。BC都是IT做形式主语，用法对头，但B的比较结构不对称，从而改变了句子的意思。

C虽然是现在完成时，但也属于现在时态的范畴，应该没问题，至少XDF说过是这样的。