Underclay
n. (煤层下的)底黏土层
🗣️ 情景例句
Before a long trip I always give my car a safety check.
远行之前，我总是会对车子进行安全检查。
Hold on.
等一会儿。
The platforms extend to a depth of over 100 feet under the sea.
平台深入海底100英尺。