1) She usually watches TV in the evening. (b)
2) She is watching TV now. (a)
3) She has been watching TV since five o'clock. (c)
4) Where's Mike? He is playing football. (a)
5) He plays football nearly every weekend. (c)
6) He has been playing football for 2 years already. (b)
7) I met Mike 3 years ago in London. I have been writing to him since then. (b)
8) We often write to each other. (a)