Optional argument
[计] 任选变元
🧩 词语组成解析
🗣️ 情景例句
I can't build a fire by rubbing two pieces of wood together.
我总不能靠着磨擦两片木柴来取火吧。
She asked me which one I'd like, and I said I didn't mind.
她问我要哪一个，我说哪一个都没有关系。[动词时态一致，这是中国人学习英语最头痛的一个问题。]
What is more, this information line operates 24 hours a day.
而且，这种"问讯线路每天工作24小时。