列举英语中现在完成时的句试!

1.Have the farmers been made to work for a long time?
2.How long have the farmers been made to work?
3.The farmers haven't been made to work for a long time.
4.The farmers have been made to work for a long time.
(^-^)呵呵,好象从头到尾变来变去只有那么一句话．自己再揣摩揣摩吧!