해커스 실전모의고사 테스트1 문법 9번문제 질문드려요..

A: I don't believe I've ever seen your kitchen this clean.

B: _________ could be, I spent houes tidying it up.



빈칸에 들어갈 답이 It being as filthy as 인데요,

분사구문 풀어쓰면 because it was as filthy as could be... 이건데...

이렇게 원급비교 as 형용사 as 뒤에 주어없이 could be가 올 수 있나요?