—i was in the US ,i made a lot of american friends.A while B although C unless D until 为啥选A

问题描述:

—i was in the US ,i made a lot of american friends.A while B although C unless D until 为啥选A

while 可以表示在什么期间,although 表示尽管,unless 为除非,until 为在什么之前,如选择d,后面应改用完成时态,故选A,指在美国期间,我交了很多美国朋友.