Lake Victoria, in Africa, is home to a group of related fishes known as cichlids. Many of these fishes are similar in appearance but have different feeding habits. What is the best method for scientists to determine conclusively whether the fish are members of a population that has a lot of variation or members of entirely different species?

• A. Study the fossil record.
• B. Compare DNA sequences because the DNA of members of the same species should be identical.
• C. Do studies on comparative anatomy, especially looking for homologous structures.
• D. All of the listed responses are correct.
• E. Observe the fish in their natural environment for possible instances of interbreeding leading to several generations of fertile offspring.