IBA is commonly used in horticulture for:
B fits best: Root initiation. Keep the Auxin Phytohormone basics straight and Root initiation stands out as the precise answer. Avoid: A) Flowering; C) Fruit ripening; D) Leaf senescence. Light and flowering items often hinge on which photoreceptor or day-length rule is in play.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.