Drivers are warned___________when they are tired.
—What did our geography teacher say? —She told us that the earth _____ around the sun.
—Lily, _____ you _____ your ticket? —Not yet!
We couldn’t wait _______ a good rest after the exam.
Although we’ve learned English for years, we have trouble _____ the foreigners.
-----How many students are there in the classroom?------_______.