A new silencing device for domestic appliances operates by producing

Can someone explain option A and Option D ans choice as well?
Are re saying lower efficiency is leading to lower electricity consumption in option choice A? and no other option choice is better than option choice A?

A) clear correct option > motor can function without having to COMPROMISE and thus making the device useful.

A new silencing device for domestic appliances operates by producing sound waves that cancel out the sound waves produced by the appliance. The device, unlike conventional silencers, actively eliminates the noise the appliance makes, and for that reason vacuum cleaners designed to incorporate the new device will operate with much lower electricity consumption than conventional vacuum cleaners.

Which one of the following, if true, most helps to explain why the new silencing device will make lower electricity consumption possible?

(A) Designers of vacuum cleaner motors typically have to compromise the motors’ efficiency in order to reduce noise production. - CORRECT. At first looks irrelevant but for it to makes sense one has to assume that less efficient motors consume less electricity. Along with that new silencing device are used thus consuming less electricity.

(B) The device runs on electricity drawn from the appliance’s main power supply. - WRONG. This is the most confusing among all the choices. It neither says, or even suggests, that electricity consumption is high nor that it is low. So, at best it is irrelevant.

(C) Conventional vacuum cleaners often use spinning brushes to loosen dirt in addition to using suction to remove dirt. - WRONG. So, looks like they consume higher electricity but it does not say so. Hence this is sort of making up so that this choice makes sense. However, doing so goes against us as it is not required and wrong to do so. Although this choice makes no sense as far as electricity consumption is concerned.

(D) Governmental standards for such domestic appliances as vacuum cleaners allow higher electricity consumption when vacuum cleaners are quieter. - WRONG. Opposite to what we are looking for.

(E) The need to incorporate silencers in conventional vacuum cleaners makes them heavier and less mobile than they might otherwise be. - WRONG. What happens later does not help us. It is irrelevant.

This is one of those questions that are easy to understand but difficult when it comes to choosing the right answer. It is somewhat like picking the best bad answer.

Answer A.