Zero Conditional

If you eat fast food,

• you gain weight.

• you gained weight.

• you would have gained weight.

If you study hard,

• you would get good grades.

• you got good grades.

• you get good grades.

When she works early,

• she wake up early.

• she woke up early.

• she wakes up early.

I always wear a jacket

• when it was cold.

• when it would be cold.

• when it will be cold.

• when it is cold.

He never buys lunch

• if he wouldn't have cash.

• if he have no cash.

• if he doesn't have cash.

• if he didn't have cash.

When you heat water,

• it boils

• it would boil.

• it has boiled.

• it will boil.

Does ice melt

• if it were in the sun?

• if it had been in the sun?

• if it will be in the sun?

• if it is in the sun?

What do you do

• if the teacher would be late?

• if the teacher is late?

• if the teacher was late?

• if the teacher had been late?

Does the computer work

• if you would have used batteries?

• if you use batteries?

• if you used batteries?

If the door is open, 

• you could come in.

• you could have come in.

• you can come in.