单词学习：hum 动词/名词
hum
/hʌm/
嗡嗡声；哼唱；活跃，繁忙
The classroom was quiet except for the soft hum of the air conditioner and Mr. Gu's gentle voice.
教室里很安静，只有空调轻柔的嗡嗡声和顾老师温和的说话声。
单词卡片
卡片已就绪
