Please choose the correct answer to the question: Arteries and veins are two important parts of the circulatory system. What is the relationship between arteries and veins?

Answer1: They work together to exchange gases. Answer2: They work together to transport nutrients. Answer3: They work independently to remove wastes. Answer4: They work independently to relay messages.

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