we ___each other since we were children.(A know B kenw C have known D had known)

问题描述:

we ___each other since we were children.(A know B kenw C have known D had known)

D,自从我们是孩子时,我们就已经知道对方了,说话人的动作从过去一直持续到现在,过去认识,现在还认识.