In light, Pfr binding to PIFs results in:
Pick B: Degradation of PIFs. Thinking through PHYTOCHROME step by step rules out the lookalikes and leaves Degradation of PIFs. Skip these: A) Activation of PIFs; C) Nuclear export of phytochrome; D) Inhibition of HY5. 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.