p51 13번이요

Paperclip Stationery was chosen as the

new office supplier, as its delivery services

better _______ the company's needs.

a) suit    b) suits   c) suiting   d) suitable

동사자리인건 알겠는데요 왜 과거형이 아니라 suit이 답인지 잘 모르겠어요

p53  36번이요

_____  in technology for creating special

effects for films have helped decrease

costs of movie production.

a) Advancing   b) To advance  c) Advanced  d) Advances

동사가 have helped라 advance에 s 가 붙은거를 택해야 하는거 같은데 왜 정답이 d죠?