Step 1: Understand Mendel's experiments.
Gregor Mendel is considered the father of genetics, and he is known for his foundational work on inheritance patterns. Mendel conducted his famous experiments on the inheritance of traits in pea plants (Pisum sativum).
Step 2: Conclusion.
Mendel's experiments were primarily performed on pea plants, as they have distinct and easily observable traits, making them ideal for genetic studies. Therefore, the correct answer is (C).