Which pressure gradient drives air into lungs?
Correct option is B, Atmospheric > Alveolar. In Cardiac Cycle and Regulation, the accurate description is Atmospheric > Alveolar, and that is what you should commit to memory. Keep the definition tight and the role clear — Atmospheric > Alveolar is the option that correctly names the structure, process, or principle asked for in Cardiac Cycle and Regulation. Then Atmospheric > Alveolar is the answer you can defend. Check yourself by covering the options and writing the answer first, then matching the letter — that builds confidence. If the wording feels dense, translate it into everyday language first, then map that plain sentence back onto Atmospheric > Alveolar.
Ref: Animal physiology is Unit 7 of the CSIR NET Life Science Syllabus, covering core body systems. It accounts for roughly 10% of the total marks in Sections B and C.