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 water given to the plant is unpolluted
C. Determine whether the earthworms benefit from being with the plant
D. Determine whether the other plant in the investigation suffers as a result of not being exposed to earthworms

C. Determine whether the earthworms benefit from being with the plant

Explanation:

To answer the question, first, we need to keep clear the concept of mutualism as an interspecies interaction.

All organisms in nature interact with other organisms in different ways. Symbiotic interactions involve a relationship between two or more organisms of different species in which one or all of them turn to be beneficiated by that relationship. These species create permanent mutual dependence.

Symbiotic interactions include mutualism, commensalism, and parasitism.

Mutualism: The interaction is favorable for both species. Their fitness increases with these interactions, although they do not need this relationship to survive. The degree of benefits might vary among species or might be equal.

In the exposed example, the student already knows that the plant got beneficiated by the earthworm's presence. Now, to test mutualism, the student needs to figure out how the earthworms are beneficiated by the plant. What are the benefits of being with the plant?. If the student can not identify any advantage, then probably, the relationship between species is not mutualism but other.

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