You had better ________some food and drinks before the field trip ________.

 –Dad, _____ we wait until the light becomes green?--Yes, we ______ . That’s the traffic rule.

—Can we run across the road now?—No, we _     . We have to wait until the light turns green.

—Could you please come to the museum with me this afternoon?—Sorry，I ________．I have to take a piano lesson at 2 pm．

—Have you seen Maragaret? The boss is looking for her everywhere.—She________the train, otherwise she would have arrived here by now.