Aidan lifts a box from the floor, carries it across the room, and places it on a high shelf. When is Aidan doing work on the box?
a. He does work only while he carries the box across the room.
b. He does work from the moment he touches the box until he lets it go.
c. He does work as he picks up the box and as he lifts it to the shelf.
d. He does work on the box at no time during this process.