A.There are no libraries in my school twenty years ago.

B.There was no gym in my school twenty years ago.

C.There was no library in my school twenty years ago.

【答案】C

【解析】

A项句子错误，B.20年前我的学校没有体育馆，C.20年前我的学校没有图书馆。根据题干语境，C项符合。故选C。