Low intercellular CO₂ concentration causes stomata to:
Pick C: Open. Thinking through STOMATA MOVEMENT step by step rules out the lookalikes and leaves Open. Skip these: A) Close; B) Remain unchanged; D) Undergo plasmolysis. 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.