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.

(B) The device runs on electricity drawn from the appliance’s main power supply.

(C) Conventional vacuum cleaners often use spinning brushes to loosen dirt in addition to using suction to remove dirt.

(D) Governmental standards for such domestic appliances as vacuum cleaners allow higher electricity consumption when vacuum cleaners are quieter.

(E) The need to incorporate silencers in conventional vacuum cleaners makes them heavier and less mobile than they might otherwise be.

agree with (A)

The conclusion here is 'vacuum cleaners that incorporate the new silencing device will operate with much lower electricity comsumption than conventional vacuum cleaners'

The premises:
New silencing device for domestic appliances operates by producing sound waves that cancel out the sound waves produced by the appliance
Device actively eliminates the noise the appliance makes.

From the premise to the conclusion, we're missing out a big chunk of assumption. We need something that tells us how the device reduces lower electricity consumption.

(A) Designers of vacuum cleaner motors typically have to compromise the motors’ efficiency in order to reduce noise production.
- If the vacuum cleaner is not efficient, then you will need to spend more time just vacuuming your house (because it's inefficient and takes a long time to finsih cleaning whatever its suppose to clean). Indirectly, you will be leaving your vacuum cleaner on for a longer period, and thus draw more electricity.

(B) The device runs on electricity drawn from the appliance’s main power supply.
- Not important.

(C) Conventional vacuum cleaners often use spinning brushes to loosen dirt in addition to using suction to remove dirt.
- Doesn't tell us a thing.

(D) Governmental standards for such domestic appliances as vacuum cleaners allow higher electricity consumption when vacuum cleaners are quieter.
- Not important.

(E) The need to incorporate silencers in conventional vacuum cleaners makes them heavier and less mobile than they might otherwise be.
- Only makes them difficult to carry around. Doesn't tell us how it reduces electricity consumption.

A it is.

My reasoning is smiple, compromising efficency means using more electric. so A is my choice

Thanks OA is A

more efficient means less power consumption and vice versa?.
oh, so deep gap.