You are presented with the quiz "Gases from what causes precipitation where the pH is 5.7 or lower?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "gases from burning coal and oil dissolving in water in the atmosphere causes acid rain" and "acid rain is precipitation which pH is 5.7 or lower". 

So, what's the best answer to the question?


 

        burning coal   