Concavation
凹度
🗣️ 情景例句
Sam, this is Susan. Sam
我是Susan。
In elementary school,the child learns to read and write.
在小学，孩子学习读写。
All the students are expert drivers, but before they drive any of the buses, they will have to pass a special test.
所有的学生都是开车的能手，但在驾驶公共汽车之前，他们必须通过一项专门测验。