Which genes constitute class B in ABC model?
AP3 and PI (B) is correct here. This is core ABC MODEL: once you know the definition or pathway step, AP3 and PI is the clear fit. The wrong ones are A) AP1 and AP2; C) AG and SEP; D) LFY and AP1. If the topic is about gradients or potentials, water/solutes move from higher to lower of the relevant quantity.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.