问题补充：
I was glad to be like my friends which all had mobile phones.I became an expert for sending fast messages.I often think my old phone will make people to laugh.Most of the time it turned off.每句只有一个
答案：
1）I was glad to be like my friends which all had mobile phones.
改为：I was glad to be like my friends （who ）all had mobile phones.
2）I became an expert for sending fast messages.
改为：I became an expert（ in ）sending fast messages.
3）I often think my old phone will make people to laugh.
改为：I often think my old phone will make people laugh.(去掉 to)
4）Most of the time it turned off.
改为：Most of the time it （was,is ）turned off.
======以下答案可供参考======
供参考答案1:
1:which改who;
2:for改of;
3:to laugh改laugh;
4:it改was
供参考答案2:
1 which --- who
2. for ---of
3. to 去掉
4 it was turned off， 中间加上was
