Question

The maths problem remained confusing to the boy although _______ over and over.

A. explaining B. being explained?

C. explained D. having explained?

Answer 1

C?

解析:

although引导让步状语从句，主从句主语一致，从句谓语动词为be动词，可将主语和谓语动词be一并省略,补全后为:...although it was explained...。