Preconcentration
n. 预选；预浓缩；预先富集
🗣️ 情景例句
Choose which you please.
先你中意的好了。
How long does it take for a letter to get to California ?
一封信到加利福尼亚要花多长时间？
When I asked him what he was doing, he smiled guiltily and then put the parcel on the desk.
当我问他正干什么时，他内疚地笑了，然后把那个大包拿到了桌上。