접속사와 동사 형태 문제 질문드려요

아래 문장에서 알맞은 답이 무엇인지 알려주세요.
( ) you were a member, you could come too. (a. that b. if c. than d. so)
( ) I was clean, I took a bath. (a. what b. as long as c. such d. even though)
I wanted to ( ) down because I was quite tired. (a. lie b. bring c. lay d. take)
While ( ) my new book, I learned something interesting. (a. to read b. read c. to reading d. reading)