sally has been swimming _____four hours 1.for about 2.since

sally has been swimming _____four hours 1.for about 2.since 按要求做题。 1. She has been swimming for 2 hours. (改为同义句) Sam has been swimming for fuor hours (改为否定句） She has been working for 20 hours Alison has been skating for five hours. 同义句转化 1.he has been eating for tow hours he has been eating_ She has been dead for about a month since she was killed in It has been three hours since he left his office.把has been 换 She has been waiting for you for two hours. has been waiting for hours和has waited for hours的区别? we have been there for about two hours. He has been practicing ___ English for two hours.