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. Thank you.