用定语从句合并下列句子。最好教我怎么并。

(1)There is a beautiful house,and in fronr of it sits a little girl.
There is a beautiful house, in fronr of which sits a little girl.

(2)Workers built shelters for the survivors.The homes of them had been destroyed.
Workers built shelters for the survivors whose homes had been destroyed.

(3)She will never forget her stay there.She found her lost son during her stay.
She will never forget her stay where She found her lost son .

(4)He completed college at 15,and I could hardly believe it.
He completed college at 15 which I could hardly believe.

(5)We arrived at noon.The play was over by then.
We arrived at noon when the play was over.

合并两个句子为定语从句，首先要明白两句的联系在哪里。
请看第一句的后半句中的it，指代的是前半句中所说的房子，那么后半句话就是用来修饰房子的，整句意思就是“有一座漂亮的房子前坐着一个小女孩”。于是句子结构出来了：前半句是主句，后半句要通过变形变成从句。
一般来讲用来修饰物的定语从句都用which来引导，
"in front of"可以提前到引导从句的词which前面。
这句话就变成了“There is a beautiful house in front of which sits a little girl.”
明白了吗？再稍加总结一下步骤：
1，找到后半句中的代词，看它指代前半句里说的啥，根据所指对象的性质，决定好用什么词来引导定语从句
2，一般情况下把那个词直接放到所指对象的后面，特殊情况下两者这间有介词

P.S. 大概说一下什么情况用什么词来引导定语从句：
修饰对象是具体物体时，用which，例：I like songs which sound beautiful. ；
如果具体物表示的是一段时间，或一个空间，前面要根据情况加介词，例：I dislike holidays during which I had to finish all my work. / I hate the house in which I was forced to study；
还有种情况，which可以指代前面整句话，例：He did it perfectly which made me admire him.
是人时，用who（此人在从句中做主语）或whom（做宾语），例：The man who killed that boy was arrested./ She was whom I saw just now.
表达“……的东西”的意思，用what，例：What makes you different makes you beautiful.
表示“某人的”或“某物的”意思，用whose，例：I pitied the girl whose parents were away.
表示某个时间点，用when，例：I saw her when she was chatting with my aunt.
引导一个需要原因的句子, 用why，例：Tell me why we have to cry.