I have waited for the bus for twenty minutes．(对画线部分提问)
________________ have you waited for the bus？
That is his old house． He lived there for twenty years． （合并为一句）
That is his old house he lived for twenty hours．
His mother will come back ____． （对划线部分提问）
will his mother come back？
Chinese doctors saved many patients all over the world． （改为被动语态）
Many patients all over the world by Chinese doctors．
David can hardly speak Chinese． （改为反意疑问句）
David can hardly speak Chinese， ？
Shanghai is the biggest city in China． （改为同义句）
Shanghai is any other city in China．