If you ...... (mix) two highly explosive chemicals, you ...... (cause) an explosion.

If you ...... (run) out of air, you ...... (be) sure to die.

If you ...... (bump) your head hard, you ...... (be) in danger of losing your memory.

If you ...... (get) shot and there ...... (be) no one to help you, you ...... (lose) your blood and ...... (die) eventually.

Bears ...... (sleep) soundly during winter if they ...... (not / disturb).

When a strong wind ...... (blow), leaves ...... (fall) down the trees.

If a river ...... (dry) out, the people in the area ...... (lose) their water supply.

If you ...... (breathe) in helium and not oxygen, you ...... (suffocate).

If somebody ...... (poison) the water supply in our area, people ...... (start) dying quickly.

If you ...... (heat) water to 100 degrees Celsius, it ...... (boil).

If you ...... (cross) an international date line, the time ...... (change) instantly.

Paper ...... (not / burn) if there ...... (be) no air.

If there ...... (be) no people in the woods, nobody ...... (hear) the sound of clapping.

If it ...... (rain), the streets ...... (be) wet.

If it ...... (not / rain) for a long time, crops ...... (get) decimated.