Optional argument
[计] 任选变元
🧩 词语组成解析
🗣️ 情景例句
We accepted their challenge to a baseball game.
我们接受了他们棒球邀请赛的挑战。
I would like to ask you a question.
我想问你一个问题。
Don't worry about that. Right now you need to stay still until help comes.
别为这事担心。现在，在有人来之前，你必须要呆着不动。