Zero
1 If people eat too much, they get fat.
2 If you touch a fire, you get burned.
3 People die if they don't eat.
First
1 If it rains, I won't go to the park.
2 If I see her, I'll tell her.
3 If I have enough money, I'll buy a new dress.
Second
1 She would travel all over the world if she were rich.
2 If I won the lottery, I would buy a big house.
3 If I had his number, I would call him.