Faculative
a. 允许的, 任意的, 兼性的, 偶发的
🗣️ 情景例句
The road toll is higher during holiday periods.
在节假日期间路桥费比以往要贵。
Opportunity only knocks once.
机不可失，时不再来。
Yes, I'm afraid so. It's getting late, and we have to be up early in the morning.
恐怕是这样。天渐渐变晚了。清晨我们得早起。