Final answer:
Reducing friction and increasing mechanical advantage enhance the efficiency of a simple machine.
Step-by-step explanation:
The efficiency of a simple machine can be enhanced by reducing friction and increasing mechanical advantage. Reducing friction helps to minimize the energy lost to heat, which improves the efficiency of the machine. Increasing mechanical advantage allows the machine to multiply the input force, resulting in a greater output force and improved efficiency. Therefore, reducing friction and increasing mechanical advantage are the factors that enhance the efficiency of a simple machine.