The pacemaker of heart is:
Answer: C) SA node. For Cardiovascular System: Heart, once you lock onto the key mechanism or definition, SA node is the clear fit. If you restate the concept in your own words, SA node is the option that correctly names the structure, process, or principle asked for in Cardiovascular System: Heart. So SA node is the clean, accurate selection. If a similar stem appears later, start from the same core fact and you will land on the same kind of answer. In class notes, highlight this same phrase next to the related diagram so the wording and the picture reinforce each other.
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.