初中英语介词短语句型转换

Mr． White began collecting coins when he was fifteen．（改为简单句）

Mr． White began collecting coins　　 the　　 of fifteen．

根据句意及首字母提示，写出可替代句中下划线部分的短语。
We will be not friends any longer if you copy my homework.  n　　　　　　
Lillian worries about her daughter when she is away, even though she has been old enough to take care of herself.   l　　　　　　
Linda kept a notebook with her in order to put down everything interesting she thought of.  w　　　　　　
They went to bed late last night playing online games. s　　　　　　
Now, many middle school students have fallen into a bad habit — smoking. A