大全sec11-20，一个关于主谓一致的问题

20.   Byron possessed powers of observation that would have made him a great anthropologist and that makes his letters as a group the rival of the best novels of the time.

(A) makes his letters as a group the rival of

(B) makes his letters as a group one to rival

(C) makes his letters a group rivaling

(D) make his letters as a group the rival of（D）

(E) make his letters a group which is the rival of

解释说从句修饰的是powers，所以谓语动词用复数。

我有个疑问，经常见到Gmat中从句就近修饰原则，如何判断从句是修饰powers还是修饰observation？尤其像本题这种情况，一旦判断错误，就会直接导致选择错误。

请NN们指点迷津，谢谢！

一般来说a of b that....的情况下，that都是指代b的，但除了语法Gmat更看重逻辑分析。

我是这么理解的。因为第一处that不是划线部分（那么它可以无法无天不遵循考试规律）。它用的又是虚拟语气，所以语法上看不出来修饰哪个词。但是如果从意思上来看，原文的that是指代powers的，因为普通的observation不可能让一个人成为一个伟大的人类学家。因此并列结构的第二个that也是修饰powers的。

另外想请问gmat现在的真题都是这样的吗，像A和D就一个区别？