A and B are doing their homework. 对A and B提问 答案who is doing their homework. 为社么是is不是are?
问题描述：
A and B are doing their homework. 对A and B提问 答案who is doing their homework. 为社么是is不是are?
答
因为后面是 their
答
因为有个人做了两个人的作业
答
不知道谁在做作业当然更不知道有几个人了,怎么确定单复数呢,这种提问一般都是用单数了,除了who are his parents这种类似的情况了