Preverb
句首助动词, 前动词(即移至句子第一个位置上的助动词)
🗣️ 情景例句
Well, that's life, isn't it?
这就是生活，不是吗？
An empty sack cannot stand upright.
空麻袋，立不直。
so they are often tempted to finish a job before setting out to keep an appointment.
因此他们常想做完一件事后再去赴约。