—Do you know sound travels very fast ?—Yes. But light travels sound.
—Are you busy this weekend? — Yes, my mother wants me ____the house.
—_____do they go to movies? — Once a month.
—I think______is not easy to draw this picture. —I think so.
—What’s the weather like in Qinghai in winter? —There is ________snow and it is ______cold.
— Excuse me. Where is the stair? — Ok. Go straight ____that door under the EXIT sign.