Bunuel
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.
Hi Let us see how it can be approached
Premise 1 : New silencing device make applications quieter.
Premise 2: Device unlike normal silencers cut the noise and make the vacuum cleaner quieter and thus consume less electricity.
The questions wants to know how it might be possible.
A can be kept aside since it talks about the motor's efficiency and that might be related to power.
B does not tell us about why the silencer maybe involved to reduce power. Similarly C and E does not say why the silencers are capable to minimize power input to the vacuum.
Only contenders are A and D . A does not specifically correlate motor efficiency and power consumption. So (D)