In which of the following cases is work being done:

(a) A boy pushing a heavy rock

(b) A boy climbing up the stairs

(c) A coolie standing with a box on his head

(d) A girl moving on the road.

Work is done in the following two cases:

(b) A boy climbing up the stairs: Work is done by the boy as the boy changes his position.

(d) A girl moving on the road: Work is done as displacement is produced by the body.