Ответ:
1.Justin has been cooking dinner for two hours now!
2.She has been buyinga present for you.
3.They have been planning their holiday for the last two weeks.
4.I have been known Jack for six years.
5.You have packing all morning.
Объяснение:
4.Неправильно: I have been knowing him for a month. Я знаю его месяц. Правильно: I have known him for a month. Я знаю его месяц.