Balkstone
含杂质的层状灰岩
🗣️ 情景例句
Chairman Mao said it is necessary to drill as much as possible.
毛主席说，反复操练是非常必要的。
Do you usually do arithmetic on Sunday?
你通常在星期日做算术吗？
He always took off his shoes and threw them on the floor.
他总是脱下鞋子，把它们丢在地板上。