If you heat water to 100C, it boils.
If there is something good on, I usually stay in and watch TV.
If I eat too much, I gain weight.

If there’s an accident, call the police.
If the road is flooded, don’t try to drive.
If you cycle on a busy road, you should wear a helmet.
If you see a bear, you shouldn’t run after it.
If there’s a fire, what should we do?