Question

---I’m sorry I forgot______the letter for you! I’m really busy these days.
---It doesn’t matter, I’ll post it myself.

1. A.
   to post
2. B.
   posting
3. C.
   post
4. D.
   posted

Answer 1

A
A forget to do sth.“忘记要做某事”；forget doing sth.“忘记做过某事”。根据句意，“我”没邮寄信件，故用to do。