Ответ:

  1. If I were you, I’d apologize.
  2. If she had known the truth, she wouldn’t have agreed.
  3. If she had seen me earlier, she would have spoken to me.
  4. If he had studied harder, he would pass the exam now.
  5. If they hadn’t missed the bus, they would have arrived on time.
  6. If I won the lottery, I’d travel around the world.
  7. If you had told me earlier, I could have helped.
  8. If the weather were better, I could have a picnic today.
  9. If she had asked me, I would have told her secret.
  10. If he weren’t so busy, he’d join us.

Использованы условные предложения второго, третьего и смешанного типов: if + Past Simple для нереального настоящего, if + Past Perfect для нереального прошлого.