Let f: r:r>r be defined by f(t)=t and let u be any non-empty open subset of r then f(u) is open s(u)is open may be closed o(u) may be osed

Option AB is correct. Continuity implies both

any doubt plz ask

so option A and B is correct

bcoz under continuity inverse image of an open set is always an open set

option D isn't correct

c is not true

For option B visit the following link. 1. https://math.stackexchange.com/questions/843909/prove-that-the-inverse-image-of-an-open-set-is-open