【题目】It is not easy to get along with him, but the friendship of his, will___________ last forever.
A. once gaining B. once gained C. while gaining D. to be gained
在线课程【答案】B
【解析】考查非谓语动词。gain与friendship之间是被动关系，once（一旦），引导条件状语从句，从句用一般现在时态的被动语态，因为与主句相同的主语和be动词可以省略，故答案为B。句意：他很难相处，但是一旦获得了他的友谊，就永远不会失去了。