Reducing friction in a machine a. decreases its actual mechanical advantage b. decreases the work output c. increases it’s efficiency d. increases it’s ideal mechanical advantage

C. Increases it’s efficiency

Explanation:

As we know that friction force is the resistive force due to relative motion of two surface. When one surface is moving relative to other surface then the motion is resisted by the interaction force between two surface which is known as friction force.

Now we can say that friction force will increase the efforts of input work due to its nature to resist the relative motion.

Now since the input force or efforts is increased then the efficiency must have its effect as we know

Now if the friction is reduced by some phenomenon then here the input efforts can be reduced so here efficiency will increase due to this.

so we can say here correct answer will be

C. Increases it’s efficiency

i think the answer is a and b

i wish you luck