Please choose the correct answer to the question: Acid rain has a pH below 5.6. This rain can damage soil, lakes, crops, and buildings. Acid rain is caused by all of the following except

Answer1: industrial emissions from factories. Answer2: coal that is burned to produce heat and power. Answer3: automobile exhaust. Answer4: nuclear power plants that produce radiation.

Answer format: answer1/answer2/answer3/answer4