A new silencing device for domestic appliances operates by producing sound waves that cancel out the sound waves produces by the appliance. The device, unlike conventional silencer, 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.
下面哪一个解释为什么省电？
A: the device runs on electricity drawn from the appliance’s main power supply.
B: designers of vacuum cleaner motors typically have to compromise the motors’ efficiency in order to reduce noise production.
The highest-ranking detectives in the city’s police department are also the most adept at solving crimes. Yet in each of the past ten years the average success rate for the city’s highest-ranking detectives in solving criminal cases has been no higher than the average success rate for its lowest-ranking detectives.
Which one of the following most helps to resolve the apparent paradox?
A those detectives in the police department who are the most adept at solving criminal cases are also those most likely to remain in the police department.
B the police department generally gives the criminal cases that it expects to be the easiest to solve to its lowest-ranking detectives.
