(-)she isn't returning a book to the library

(?)is she returning a book to the library?

(-)they aren't waiting for us

(?)are they waiting for us?

(-)She isn't finishing the math homework

(?)is she finishing the math homework?

(-)they aren't studying in the library

(?)are they studying in the library?

(-)he isn't having a meeting in the teacher room

(?)is he having a meeting in the teacher room?

(-)she isn't meeting the principal

(?)is she meeting the principal?

(-)they aren't talking about the football match

(?)are they talking about the football match?

(-)he isn't buying something in the school Co-op

(?)is he buying something in the school Co-op?

(-)we aren't practicing English

(?)are we practicing English?

Penjelasan:

aren't = are not

isn't = is not