Ответ:
1. If you stay in the sun for a long, you can get very sunburn.
2. If a computer have a big memory, it runs faster.
3. If Rebecca tells me the whole story, I will be able to advise what to do.
4. If Tom doesn't have time to say hello, I won't either.
5. My workplace would be more comfortable if I wasn't in the room with 3 more colleagues.
6. If he had looked to the weather forecast, she wouldn't leave.
7. If I had watched the film before, I would have forgotten it anyway.
8. If Jenny had got up early, she wouldn't have been late for school.