Answer:
In this experiment, the group of rats that is fed the high-protein diet is experimental group; the group that receives ordinary rat chow is control group.
Explanation:
A scientific experiment comprises of a control group and an experimental group.
An experimental group comprises of a dependent variable and an independent variable. The protein rich diet is the independent variable and the running performance of the rats is the dependent variable.
A control group can be described as the experimental group in which no changes are made and the results in the experimental group are analyzed by comparing the changes with the control group.