Schwann cells are found in :-
1. Myelinated nerve fibre
2. Unmyelinated nerve fibre
3. Both (1) and (2)
4. None

Dear student, Some nerve fibres are completely surrounded and insulated by a myelin sheath which is fatty in nature. This myelin sheath is formed by another type of cell called Schwann cell. The cell surface membrane of the Schwann cells get extended and wraps itself around the nerve fibre. This extension forms the myelin sheath and is mainly lipid, lacking the protein which are normally found in membranes. They keep peripheral Nerve cells that include both myelinated and u myelinated cells alive. Hence option 3 is correct. Thanks and regards.