Here's a problem to solve: A student is pushing a 20-kilogram box up a ramp. Which change will require the student to use less force to push the box?

Among the 4 following options, which is the correct answer?

- A: increasing the mass of the box
 
- B: decreasing the length of the ramp
 
- C: decreasing the steepness of the ramp
 
- D: increasing the friction on the surface of the box
 