Underdrain
n. 阴沟, 地下沟道, 盲沟, 暗渠
🗣️ 情景例句
Yes, indeed.
对 ，正需要。
His courage is a lesson to us.
他很有勇气，是我们大家的榜样。
Now move the hand to and fro and around but not up and down.
然后把手前后左右以及旋转摆动，但不要上下摆动。