根据对话内容, 在每个空白处填入一个适当的句子, 使对话完整、合乎情境。
A：____?
B：No. It is a photo of my uncle's family.
A：____?
B：They are in London.
A：____?
B：Yes. My cousin's name is Cui Tong.
A：____?
B：Thirteen.
A：____ ?
B：No. he is in Grade 8. But the girl is in Grade 7.
A：Oh. I see. She is his sister
⑤Mg+2．