When Mendel crossed true breeding yellow and green pea plants, what made him conclude that the green variant is the recessive trait?

• A. He observed it in a few peas in the F1 progeny
• B. It became the dominating trait in the F1 progeny
• C. The trait was not observed both in F1 and F2 progeny
• D. It showed up only in the F2 progeny

Answer: (D)