Next time put such questions in the physics section in order to get the right answer quikly. According to the facts that he puts out 100 foot-pounds of energy dragging a box up an incline and friction uses 20 foot-pounds of that energy while he gets only 80 foot-pounds of energy for his effort, I would say that it is definitely the first option - declarative. I do hope it will help you in your homework. Regards.
