1.We have known each other for a long time.（改为一般疑问句）
_Have___ you _known___ each other for a long time.
2.He flew to New York.（改为现在完成时）
He __has__ __flown__ to New York.
3.They have stayed in China (for 2 years).（对括号部分提问）
_How___ _long___ have they stayed in China?
4.He has kept the book for 3 weeks.（改为否定句）
He _hasn't___ _kept___ the book for 3 weeks.
5.We won't go to the park because it's raining heavily now.（改为同义句）
We won't go to the park _becasue___ _of___ the heavy rain.