Ответ: 1. The trains all would stop if it snowed heavily. 2. If you went out in cold weather without a coat, you would catch a cold. 3. If I saw a cheap second- hand car, I would buy it. 4. If you ate well and exercised regularly, you would live 100 years. 5. You would have had stomach ache if you had eaten too much of that cake. 6. If it rains this afternoon, I shall take my umbrella. 7. If you did not drive carefully, you would have an accident. 8. If you study for a higher qualification, you will get a better job next year. 9. If you sent the letter by first class mail, it would get there the following day. 10. If the weather is fine, we shall go for a picnic.