They did everything in their power to save the building dating back to the Qing Dynasty, but their efforts were _______.
He said he ____ an American before.
Eight students ____ ten in our class are League members.
----- When are you _____ your next exams? ----- Next month.
The book-store _____ open until 8 at night every day.
This task is _____ for us. We need ______ people.