Class A + Class B gene expression specifies:
Pick B: Petal. Thinking through ABC MODEL step by step rules out the lookalikes and leaves Petal. Skip these: A) Sepal; C) Stamen; D) Carpel. For hormones and genes, match the molecule or gene to its real role, not a neighboring pathway.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.