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Use the Present Perfect Continuous and for or since for each of the following situations.
Пример:
My friend started reading an interesting book a month ago. He is still reading it. He has been reading the book since last month.

c.Viktor began writing a letter to his pen-friend in the U.K.last week and he is still writing it.__________________since last week.

d.Omars father started driving his car when he was 20 and he is still driving it._______________since he was 20.