Please choose the correct answer to the question: What is the best way for a marine scientist to determine the eating habits of sharks?

Answer1: Tag one shark and monitor its eating habits for one day. Answer2: Tag one shark and monitor its eating habits for one year. Answer3: Tag several sharks and monitor their eating habits for one day. Answer4: Tag several sharks and monitor their eating habits for one year.

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