Question

the passage below describes an experiment.
mint plants
neil grew twelve mint plants on his back porch. he grew each plant in its own pot. neil noticed that his plants did not grow many leaves, and he wanted to see if earthworms could help them grow more. neil divided his twelve plants into three equal groups. he added three earthworms to the soil in each of the first four pots and six earthworms to the soil in each of next four pots. he did not add any earthworms to the remaining four pots. two months later, he counted the number of leaves on each of the twelve plants.
in this experiment, which were part of a control group?
the mint plants that did not get earthworms
the mint plants that got three earthworms

Explanation:

A control group in an experiment is the group that is not exposed to the variable being tested (here, earthworms) to serve as a baseline for comparison. Neil's experiment tests the effect of earthworms on mint leaf growth, so the group without earthworms is the control.

Answer:

the mint plants that did not get earthworms