4. If the water temperature increases, some aquatic creatures will be unable to reproduce.

5. If farmers didn't use much chemical fertilizer, the soil wouldn't be polluted.

6. Since the parents were exposed to radiation, their children have birth defects.

4. The water temperature increases. Some aquatic creatures are unable to reproduce. (Rewrite, using “Conditional sentence type 1”)

--> If the water temperature increases, some aquatic creatures will be unable to reproduce.

5. Farmers use much chemical fertilizer, so the soil is polluted.( Rewrite, using “Conditional sentence type 2”)

--> If farmers used much chemical fertilizer, the soil would be polluted.

6. Their children have birth defects. The parents were exposed to radiation. ( Combine the sentences, using “since”)

--> Since the parents were exposed to radiation, their children have birth defects.