题目内容：

Twenty years ___long for us but only a short time in human history A is B are Cwas Dwere

优质解答

Twenty years ___long for us but only a short time in human history A is B are Cwas Dwere
选A
twenty years看成一个整体
谓语动词用单数
又因为说的是一个事实
所以用一般现在时