Sympathetic stimulation of heart increases rate mainly by:
Go with B — Increasing Ca²⁺ influx. Within Cardiac Cycle and Regulation, that statement lines up with the standard definition and the usual exam wording you’ll see. In plain terms, the functional job described in the stem is exactly what Increasing Ca²⁺ influx does in Cardiac Cycle and Regulation. Holding that picture in mind makes Increasing Ca²⁺ influx feel natural rather than something you only memorise. Link the term to a real body example (organ, tissue, or ion flow) so the idea stays concrete under exam pressure. A short mental diagram helps — start from stimulus or structure, follow the pathway, and stop at the functional result described by Increasing Ca²⁺ influx.
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.