Mobile sources
[经] 机动的来源
🧩 词语组成解析
n. 输入源；发起者；来源（source的复数）
🗣️ 情景例句
Where shall I put my signature?
我签在哪儿呀？
The police crept up from behind and took the gangster by surprise.
警察悄悄从背后绕过去，出其不意地将歹徒逮捕。
That's difficult!
那就难啦！