Ethylene insensitive mutants include:
Pick B: etr1. Thinking through Ethylene step by step rules out the lookalikes and leaves etr1. Skip these: A) ctr1; C) ebf1 ebf2; D) ein3 overexpression. 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.