Where are the Black family?——They ________ the new zoo.

Not until he questioned the manager several times ___________ that the engineer-in-chief had gone to an important meeting.

In the past, ice used to ______ used to ______ the air in a room.

Helen has two sisters and a brother. Her brother is working, but _________her sisters are still at school.

What’s favorite subject?—My favorite subject is math.