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？

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錯在 increasing不能修飾cold 變成去修飾weather 但天氣並不會逐漸增加

e是說越來越冷的天氣 這樣就對了 後面又簡潔 對的一蹋糊塗

另外用what may have been也太囉唆了 may 後面看到要用完成式又用被動
就變成may have been xxx已經夠長了 何須搞的更長來自尋煩惱