The levels of radioactive pollution decrease. We switch from nuclear power to renewable energy sources.
=>If the levels of radioactive pollution decrease, we'll switch from nuclear power to renewable energy sources.
=>If we switch from nuclear power to renewable energy sources, the levels of radioactive pollution will decrease.
Theo mình, về nghĩa thì câu 2 ổn hơn bạn hỏi nhé!
Chúc bạn học tốt!