[求助]这个语法现象不太明白，请大家指教

大全885 03-21.   At
the time of the Mexican agrarian revolution, the most radical faction, that of
Zapata and his followers, proposed a return to communal ownership of land,
to what had been a pre-Columbian form of ownership respected by the Spaniards.

(A) land, to what
had been a pre-Columbian form of ownership respected by the Spaniards

(B) land, a form
of ownership of the pre-Columbians and respected by the Spaniards

(C) land,
respected by the Spaniards and a pre-Columbian form of ownership

(D) land in which
a pre-Columbian form of ownership was respected by the Spaniards（A）

(E) land that had
been a pre-Columbian form of ownership respected by the Spaniards

正选是A,同意，但是A的语法结构不明白，前人说是

to what
had been a pre-Columbian form of ownership respected by the Spaniards是return的同位语，不是很明白，请指教谢谢，总觉得插入语这个东东很神奇，请指教

这道题目中A选项的what引导的从句是作为同位语出现的，而一般同位语出现都是正确答案的标志，因为它很简洁，指代对象也很清楚。楼主可能会疑惑为何加了个to，其实这个to正是一个正确答案的标志，它符合了介词尽量补出的原则。由于前面的结构是to communal ownership of land，为了使what修饰communal ownership,所以前面补了个to ,这样就消除了任何歧义，what只能修饰ownership了。B选项and前后不对称，前面是一个名词而后面是一个分词，C选项前面是个分词后面是个名词也不对称，所以都错了。D和E语法与逻辑没有大问题，但是考虑到它们都用了定语从句，而A中的同位语是优于定语从句的，更何况A还用了介词尽量补出的原则，所以答案选A。

由上面的分析可以看出，GMAT语法的相对正确不仅包括从几个都是错误的选项中去选出一个错误相对来说比较轻微的选项作为正确答案，还包括从几个都是正确的选项中找出一个最符合正确答案特征的选项作为正确答案，这样就体现了GMAT考试的能力性，增加了它的难度。