把下列每对句子合并成含有定语从句的主从复合句：
6.The letter is from my sister.I received it yesterday.
7.The play was wonderful.We saw it last night.
8.The train was late.It was going to Nanning.
9.The boy is my brother.He was here a minute ago.
10.The tree is quite tall.He is climbing it.
11.Here is the girl.Her brother works in this shop.
12.That’s the child.We were looking at his drawing just now.
13.This is the boy.His sister is a famous singer.
14.I want to talk to the boys.Their homework haven’t been handed in.
15.Is that the woman?Her daughter is in my class.
16.He used to live in a big house.In front of it grew many banana trees.
17.They passed a factory.At the back of the factory there were rice fields.
18.The soldier ran to the building.On the top of it flew a flag.
19.In the evening they arrived at a hill.At the foot of the hill there was a temple.
20.She came into a big room.In the middle of it stood a large table.