含有be动词的陈述句变一般疑问句时,只需要把be动词提前至句首,然后注意一些人称变化（即第一人称和第二人称互相转换）即可.
答案：
1.That is your mother.
变成：Is that my mother?
2.These are her books.
变成：Are these her books?
3.These are his brothers.
变成：Are these his brothers?
4.Those are his (my?)
此句楼主打字有误,大致答案是：Are those his...