Mutation in class B genes results in absence of:
Pick B: Petals and stamens. Thinking through ABC MODEL step by step rules out the lookalikes and leaves Petals and stamens. Skip these: A) Sepals and petals; C) Stamens and carpels; D) Sepals only. 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.