为你解答.
1 They have been here (since 2000). 对括号内提问
（How long） have they been here?
2.The old man （died） last year. He （is dead） for a year. (die,动词填空)
3.This factory opened twenty years ago.(同义句转换)
This factory （has been open） for twenty years.
4.Miss Gao left an hour ago.（同义句转换）
Miss Gao （has been away） for an hour.
把下面的句子变为被动语态：
1 We can finish the work in two days.
The work （can be finished） in two days.
2.They produce silk in Suzhou.
Silk （is produced） in Suzhou.
3.The children will sing an English song.
An English song （will be sung） by the children.