_____you have already known each other.I won't introduce you to her.A If B since C until D,Unless

问题描述:

_____you have already known each other.I won't introduce you to her.A If B since C until D,Unless
请说下理由.

后面说不介绍,前面就应该是说因为已经认识,所以要填“因为”,这里只有B 符合