The father and the son entered the tiger area _______ two doors were open at the time.Suddenly five tigers appeared, one of which killed the father.
184. There's no wind now. We can't _______ kites on the playground.
183. This plan will help to _______ two birds with one stone.
182. In the time of great trouble, the soldiers _______ their spirits by singing.
181. The old man told us most of the story, but _______ the part about the murder.
180. The monkey came down and _______ onto the elephants back.