Paneth cells are mainly involved in:
Antimicrobial defense (C) is the right choice. This sits at the heart of Digestive System: the wording points straight to what is happening in the tissue or organ system. A useful study habit is to ask what the structure or process is for: the functional job described in the stem is exactly what Antimicrobial defense does in Digestive System. That reasoning supports Antimicrobial defense. One solid sentence about why this works is enough for recall — you do not need a long essay for every MCQ. When you practise, cover the choices first, write Antimicrobial defense from memory, then reveal the letter — that habit builds real recall for Digestive System.
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.