a) Type 1
1. If we recycle, we will save natural resources.
2. If you are careful, you won't fall over the rocks.
3. If you are careless, you'll break the vase.
4. If Ha works hard, she can pass the exam.
b) Type 2
1. If I knew the answer, I could give it to you.
2. If Mrs. Green had money, she would travel around the world.
3. If you had a pen, you could write down the address.
4. If the number on those houses in this apartment were clearly numbered, I could find my cousin's house.
c) Mixed practice
1. If I knew the answer, I could tell you. (2)
2. If you are calm, you won't make any wrong decision. (1)
3. If you don't leave immediately, I will call the policeman. (1)
4. If I knew her number, I would ring her up. (2)
