1. If Tom had been honest, he would have returned the money.
2. If I hadn't come along, he would have been attacked.
3. If I had known how difficult it would be, I wouldn't have taken the job.
Giải thích: câu điều kiện loại 3: diễn tả hành động trái ngược với quá khứ
If+ S1+ had+ PII...., S2+ would have PII.........