pulley. lever. wedge. screw.
I gave my students this multiple choice question: Many common hand tools create a mechanical advantage by using the basic principles found in simple machines. For example, a screwdriver uses the principles of the wheel and axle. In order to increase gripping force, pliers use the principle demonstrated in the

Only one answer is correct among these 4 choices:
- pulley.
- lever.
- wedge.
- screw.

Could you tell me which one is correct?

lever.