The Marshal stepped over the vacuum-cleaner and stumped out of the room.元帅迈过真空吸尘器，脚步沉重地走出了房间。He could hear the whirr of a vacuum cleaner.他能听到真空吸尘器的嗡嗡声。I went down on one knee to plug in the vacuum cleaner.我单腿跪下插上吸尘器插头....
铜是热和电的良导体.Copper is a good medium for the conduction of heat and electricity.木头是热和电的不良导体.Wood is a poor conductor of heat and electricity.铜是电的良导体.Copper conducts electricity well....