Answer:
Option(B).= Normal
Step-by-step explanation:
Normal force is a type of contact force which is perpendicular to surface of contact of objects like the surface of chair that prevents us from falling downwards or that of table that prevents an object from falling from it.
By Newton's third law, every force has an equal and opposite reaction so when we sit on a chair the force of gravity pulls us down which is thus the force we apply on chair due to the pull and because of it, the chair applies an equal normal force on us which prevents us from falling down.