请教高手英语语法问题~~谢谢~~

Question

1.The boy and the girl each has/have their own toys
为何用have,不用has
2.That was because/when I was thirteen I entered the No.1 Middle School.
为何用because，不用when
3.They don't know what/who their parents are?
为何不用who
4.Mary wrote an article on the team why/that had failed to win the game.
为何用why
5.Where I live there are plenty of sheep.
there可不可以省略，为什么
6. Wherever there is oppression, there is resistance.
分析一下从句的结构，there的用法
谢谢~~~~

Answer 1

1，同位语
2，表语从句，从句中句子成分完整，根据句意选because。
3，宾语从句中what作表语，意思是"……的人"，who做主语，不做表语
4，定语 从句主语选that
5，不能，这是完整的句子，省略后句子没主语
6，前半句是状语从句，整句话是非限制性定语从句，可以理解为固定搭配