补充 128 来看看

128. During the Renaissance, scholars were uncertain as to the location of Troy, and by the eighteenth century many historians doubted that Troy had ever existed.

(A) doubted that Troy had ever existed

(B) doubt that Troy has ever existed

(C) were in doubt as to the existence of Troy

(D) were doubtful concerning Troy’s existence（A）

(E) had doubts about Troy’s ever existing

首先选了C 发现和答案a 不一样查字典 ,但是M-W字典是这样说的 doubt: transitive senses  
1 archaic    a : FEAR  b : SUSPECT 2 : to be in doubt about *he doubts everyone's word*  然后我又查了 as to :  AS FOR, ABOUT *at a loss as to how to explain the error*  

(C) were in doubt as to the existence of Troy 这样 C 在语法结构上就没有一点错了. 并且和前文很匹配. 时态也没错.那么为什么他不对呢???  好像前人没有人能解释这一点的啊~~  

A，C，D从语法上都很难挑出错，选项C不如D与前面平行，D的表语是adj，C的表语是介词短语。但C和D都有同样的毛病：existence没有表达出had existed的时态含义。 所以C和D的逻辑意思不准确。

open to discussion......