高考英语|动词在句首是什么句式，什么时候加ing？

Question

Look forward to your reply with the least possible delay.
Expecting to hear from you as soon as possible.

为什么第一句look不是looking
而第二句不是expect

Answer 1

Look forward to your reply with the least possible delay. 期待您的回复，尽可能少的延误。

此句是祈使句（以动词原形开头的句子：Do sth. ），表示请求、命令、警告、静止等。

(I am) Expecting to hear from you as soon as possible. (我正在）期待着尽快收到您的来信。

此句省去了主语I和be动词am, 是现在进行时。