What do these sentences mean and what's the difference?
1. It is five years since I have lived here. (I haven't lived here for five years??)
2. It's been two weeks since he was on a business trip.(Does he returen from his business trip??)
3. It's been two weeks since he has been on a business trip.
4. I haven't heard from him since he lived in London.
5. I haven't heard from him since he has lived in London.