Based on the law of conservation of energy how can we reasonably and pros of machines ability to do work ?

According to law of conservation of energy " energy neither created nor it can be destroyed" but can be changed from one form to another form.

By considering the above statement, if we want to increase the ability to do more work of a machine the friction between mating parts has to be reduced.

Due to the friction the energy lost is in the form of heat. Whenever the parts of the machine are under the motion with kinetic energy some of the energy transfers as heat energy and the energy loss is equal to the work done by the friction force.

So, if we reduce the friction, the machine's work output will be increased, thereby efficiency also increases.  

the answer to your question is high voltage and high currency

answer: option c.

explanation: