1. Robert is sorry now that he didn't accept the job.

⇒ Robert now wishes he had accepted the job.

2. Experts think that all dogs evolved from wolves.

⇒ All dogs are thought (by experts) to have evolved from wolves.

3. Richard only took over the family business because his father decided to retire early.

⇒ But for his father's early retirement, Richard wouldn't have taken over the family business.

4. She is now leading a normal life as a result of all the support she received from social workers.

⇒ If she didn't receive all the support from social workers, she wouldn't be leading a normal life now.

5. If I have plenty of warning, I'll willingly baby-sit for you.

⇒ Provided you give me plenty of warning, I'll willingly baby-sit for you.

6. I was exasperated when the appointment was cancelled once again.
⇒ Imagine my exasperation when the appointment was cancelled once again.

7. The only reason the party was a success was that a famous film star attended.

⇒ Had it not been for the famous film star’s attendance, the party wouldn’t have been a success.

8. If Cathy hadn't been so mean, we'd have had a really good time.

⇒ But for the fact that Cathy hadn't been so mean, we'd have had a really good time.

9. I can't imagine myself ever singing in public.

⇒ I would never sing in public.

10. I wish I'd paid more attention to his warnings.

⇒ I regret not paying much attention to the warnings.

11. It is a shame he had to leave before the end of the show.

⇒ I wish he hadn't have to leave before the end of the show.

12. Your car might break down on the rough mountain road, so take plenty of spare parts.

⇒ In case your car breaks down on the rough mountain road,take plenty of spare parts.