托福语法题，求详解，谢谢

来源：百度知道 编辑：UC知道 时间：2024/05/26 06:32:07
The telegraph, invented in the mid-nineteenth century, remained even into the 1970's-------of telecommunication.

(A) a principal system
(B) a system was principal
(C) that was a principal system
(D) a principal system when

选C，俩逗号中间可看作插入语忽略
The telegraph remained even into the 1970's
主谓宾结构完整
那后面就是宾补或从句，选项C符合
(A) a principal system（冠词不接在名词后）
(B) a system was principal（不可以接介词of）
(D) a principal system when（关系代词不可以接介词）

even into the 1970's是时间状语，提前了，放在后面应该是remained a princinpal system of
telecommunication even into the 1970's.

C