857 There is speculation that increasing cold weather was what may have been responsible for the Anasazi move from Mesa Verde to sites in other canyons.

(A) that increasing cold weather was what may have been

(B) whether increasing cold weather was what was

(C) that increasingly cold weather was what had been

(D) whether increasingly cold weather may have been what was（E）

(E) that increasingly cold weather may have been

请问C错在哪里？

was 和 had been 同指一个东西，但时态不一致。

1、过去完成时单独使用，不正确

2、题干中表示可能的情态动词一般不要省略，省略后改变原句意思了

3、was what had been太罗嗦了

A错在 increasing不能修饰cold 变成去修饰weather 但天气并不会逐渐增加

e是说越來越冷的天气 这样就对了 后面又简洁 对的一塌糊涂

另外用what may have been也太罗嗦了 may 后面看到要用完成式又用被动就变成may have been xxx已经夠长了 何須搞的更长来自寻烦恼

My q1:may不是虚拟语气那是什么?只是表达可能性的情态动词?

My q2非画线部分: responsible for the Anasazi move 一般现在时

from Mesa Verde to sites in other canyons.

responsible for后面加的是个句子而且没有that宾语从句省了that