Please choose the correct answer to the question: When sodium hydroxide reacts with a copper nitrate solution, the reaction vessel needs to be kept on ice to slow down the reaction. What best describes this reaction?

Answer1: an exothermic reaction that absorbs energy Answer2: an exothermic reaction that releases energy Answer3: an endothermic reaction that absorbs energy Answer4: an endothermic reaction that releases energy

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