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
I'll go to him.
我去。
I'm sorry to have kept you waiting.
很抱歉，让你久等了。[分词作状语]
I've just called the Frist Aid Centre.
我刚才已经给急救中心打了电话。