1. We must leave now, or we will miss the plane.
- If we don't leave now, we will miss the plane.
2. Be careful or you may fall.
→ If you are not careful, you may fall.
3. Hurry up or we'll be late for the concert.
→ If we don't hurry up, we'll be late for the concert.
4. Our sources of energy will soon end if we don't try to save them.
- Unless we try to save our sources of energy, they will soon end
5. You will catch a cold if you don't keep your feet dry.
Unless you keep your feet dry, you will catch a cold.