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

解释如下:

A项结构为...faction...proposed a return to communal ownership of land, to what had been a pre-Columbian form of ownership respected by the Spaniards.

其中,to what 结构是a return to ...的同位语(省略了a return,这种形式较为古老---引自白勇语法书),正确;

B项a form of ownership of the pre-Columbians和 respected by the Spaniards同时修饰land,前面的结构逻辑不通,后面的结构未反映出这种ownership在主句动词发生之前得到S人的推崇;且两个结构语法功能不能一致,无法并列;

C项错误同B;

D项错误的指出主从发生在同一时间范畴之内;

E项虽然表达了时间上的先后顺序,但在逻辑上存在错误,即土地本身并不是一种所有权形式.

BC中似乎中心词是of后面的那个词

但是

SEC C 24. The endurance and consistency of baseball star Lou Gehrig, known as “The Iron Horse,” are legendary.
(A) The endurance and consistency of baseball star Lou Gehrig, known as “The Iron Horse,” are legendary.
(B) The endurance and consistency of Lou Gehrig, a baseball star know as “The Iron Horse,” is legendary.
(C) Known as “The Iron Horse,” the endurance and consistency of Lou Gehrig, the baseball star, is legendary.
(D) The reason baseball star Lou Gehrig is known as “The Iron Horse” is because of his legendary endurance and consistency.
(E) Known as “The Iron Horse,” baseball star Lou Gehrig’s endurance and consistency are legendary.

中又不知道OF 中心词是那个，上面这道题至今没有明确的答案

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大家讨论下吧～～～

A of B结构里面两个都可能成为中心词.

SEC C 24应该选A的，B中除了主谓一致的错误外，同位语修饰错误了，同位语解释的是整个名词，不是名短中某个词.