Polypodiatae
水龙骨纲
🗣️ 情景例句
When you have nothing to do, time goes slowly.
你没事做时，时间便过得很慢。
To operate a steam locomotive
驾驶蒸汽机车
but the paper was wrapped round a drum which rotated slowly.
根但是纸是卷在慢慢旋转的圆筒上的。