He is not easy-going, but his trust in his friends will last forever once .
A. to be gained
B. is gained
C. being gained
D. it is gained
网友回答
A. to be gained
B. is gained
C. being gained
(答案→)D. it is gained
解析：考查状语从句的省略式：当主从句的主语一致的时候，可以省略从句的主语和be动词，句意：他不是很随和，但是他对朋友的信任一旦获得就永远不会消失。这里的it指代his trust in his friends，如果省略的话，应该是填gained，ABC都不对，所以就不用省略式，选D。