PHOT2 is mainly required for phototropism under:
B fits best: High light. Keep the Phototropin+All basics straight and High light stands out as the precise answer. Avoid: A) Low light; C) Red light; D) Darkness. 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.