A student performed an investigation in which two ivy plants were planted in two separate containers. One of the containers had earthworms mixed in with the soil, and the other container had soil and no earthworms. The plants were given the same amount of water and exposed to the same amount of sunlight. The student observed that after several weeks of growth, the plant exposed to earthworms appeared to be healthier and exhibited more growth. To conclude that the relationship between the plant and the earthworm is an example of mutualism, the student must perform follow-up investigations that do which of the following? A Determine whether the earthworms damage the soil in any way B Determine whether the earthworms benefit from being with the plant C Determine whether the water given to the plant is unpolluted D Determine whether the other plant in the investigation suffers as a result of not being exposed to earthworms