A Researcher Wants to See If a Protein-Enriched Diet Will

A researcher wants to see if a protein-enriched diet will enhance the maze-running performance of rats. One group of rats is fed the high-protein diet for the duration of the study; the other group continues to receive ordinary rat chow. What types of groups are represented in this study?

A) The high-protein group is an experimental group; the rat chow group is a control group.
B) Both groups are experimental groups.
C) Both groups are control groups.
D) The high-protein group is a control group; the rat chow group is an experimental group.