It was so dark outside that the little child ________ go out by himself. 

--It is really fun to hike and I often go hiking in the forest.--But hiking alone in the forest ______ be very dangerous.

—I don’t care what my teachers think．—Well，you________．

Henry _____be at home because he phoned me from his office just now.

—Have you decided when to leave for Australia?—Not yet. We _________ set off at the end of this month.