This problem may lead to more serious ones if_______ unsolved.

问题描述:

This problem may lead to more serious ones if_______ unsolved.
A.remained B.left 选什么 根据是什么?

应该选B,因为remain的意思是保留,保持,选它的话主语应该是“问题”,这个地方它的形式应该是remaining,所以应该选left,主语是人,问题是被人遗留而保持没解决的状态.