has been waiting for hours和has waited for hours的区别?

has been waiting for hours和has waited for hours的区别? She has been waiting for you for two hours. has been waited 和has been waiting 有什么区别? She has been working for 20 hours Alison has been skating for five hours. 对画线部分提问 she has been working for 2 hours for 2 hours 画线 ① he has been working for five hours for five hours用它提问、 He has been practicing ___ English for two hours. Sam has been skating for four hours.改为否定句 has been on the phone for several hours The meeting has been _____ (结束)for 2 hours. The meeting has been off for two hours.It______since_______.