Which process directly causes guard cell swelling?
Pick B: Endosmosis of water. Thinking through STOMATA MOVEMENT step by step rules out the lookalikes and leaves Endosmosis of water. Skip these: A) Active ion pumping; C) Diffusion of gases; D) Photosynthesis. 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.