Please choose the correct answer to the question: Students conducted an investigation with green bananas. They hypothesized that an onion placed near a banana could increase the rate at which the banana ripened. They placed one onion and one banana in each of three containers. In a fourth container they placed a banana, but no onion. Which statement best explains why the onion was left out of the fourth container?

Answer1: The onion would contaminate the fourth trial. Answer2: The container without the onion is the control. Answer3: Three containers with onions are enough to conduct the test. Answer4: The container without the onion is the independent variable.

Answer format: answer1/answer2/answer3/answer4