A man, of mass m,

according to question,

When a man of mass m ,climbs up the staircase of height L

work done by gravitational force on man =-mgL

work done by muscular forces=- (work done against gravitational

force) =mgL

∴ work done by all the forces =mgL-mgL=0

as the point of application of contact forces does not move

so, work done is zero.

option (b, d) is correct.