The correct option is A 10 N, upward direction
Given:
Weight of body in air (w1) = 50 N
Weight of body when immersed in water (w2) = 40 N
We know that, buoyant force (FB) always acts on the body in the upward direction, and the value of buoyant force is equal to loss in weight of the immersed body in water (w).
∴w=FB=w1−w2
⇒FB=50−40
⇒FB=10 N