Perilymph is present in:
Scala vestibuli and scala tympani (C) is the right choice. This sits at the heart of Sensory System Ear Physiology: 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: location matters here: Scala vestibuli and scala tympani is the structure or site that matches the description. That reasoning supports Scala vestibuli and scala tympani. 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 Scala vestibuli and scala tympani from memory, then reveal the letter — that habit builds real recall for Sensory System Ear Physiology.
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.