Defined as how much energy it takes to perform a specific amount of work.

a.) machine
b.) friction
c.) efficiency
d.) mechanical advantage

Defined as how much energy it takes to perform a specific amount of work.

B. Friction

I think the best answer from the choices listed above is option B. Friction force is defined as how much energy it takes to perform a specific amount of work since it is the only force among the choices listed above. Hope this answers the question.

Ithink your answer is d