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题库 / Prep2007E2-CR-14
Most household appliances use electricity only when in use. Many microwave ovens, however, have built-in clocks and so use some electricity even when they are not in use. The clocks each consume about 45 kilowatt-hours per year. Therefore, households whose microwave oven has no built-in clock use 45 kilowatt-hours per year less, on average, than do comparable households whose microwave oven is otherwise similar but has a built-in clock.
Which of the following is an assumption on which the argument depends?
Households that do not have a microwave oven use less energy per year, on average, than do households that have a microwave oven.
Microwave ovens with a built-in clock do not generally cost more to buy than microwave ovens without a built-in clock.
All households that have a microwave oven also have either a gas oven or a conventional electric oven.
Households whose microwave oven does not have a built-in clock are no more likely to have a separate electric clock plugged in than households whose microwave oven has one.
There are more households that have a microwave oven with a built-in clock than there are households that have a microwave oven without a built-in clock.
类比推理，无clock的微波炉比有clock的微波炉少耗电45千瓦 -》无clock微波炉的家庭比有clock微波炉的家庭少耗电45千瓦。
区别：无clock微波炉的家庭是否有别的耗电电器？
Households whose microwave oven does not have a built-in clock are no more likely to have a separate electric clock plugged in （插上电源）than households whose microwave oven has one.
没有内置钟微波炉的家庭不需要外部计时器