Please choose the correct answer to the question: Termites eat wood but cannot digest it. Protozoans live in the termites' stomachs and use enzymes to break down the wood. The digested wood provides nutrition for both the termites and the protozoans. What type of relationship is this?

Answer1: mutualism Answer2: parasitism Answer3: predation Answer4: commensalism

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