[求助]大全-1-18

ninaluan

17.   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.（A）

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

我怎么觉得A像支持的呢?

lugubrious

它不是就要支持吗.

A这样就可以不应为怕噪音,而限制吸尘器的功率了.