Variation problem
[计] 变分问题
🧩 词语组成解析
🗣️ 情景例句
It's a bet.
一言为定。
When do you get up everyday?
每天你几点起床？
It was necessary, therefore, to invent instruments that neither slumbered nor slept.
因此，有必要发明一种仪器，既不打盹儿，也不睡觉。