Please choose the correct answer to the question: Signs in many stores and restaurants warn that microwaves are in use. What is the main reason for this warning?

Answer1: Some people do not like food cooked in microwave ovens. Answer2: Microwaves sometimes affect people's sense of sight. Answer3: Microwaves sometimes cause hair or teeth to fall out. Answer4: Some people have pacemakers that may be affected by microwaves.

Answer format: answer1/answer2/answer3/answer4
Answer: answer4