The boy slipped out of the room and headed for the swimming pool without his parents' _____.
Having been ill in bed for nearly a month, he had problems __________ the exam.
It was so dark that he __________.
The Wangs are considering __________ to Huangshan for a trip at five tomorrow morning.
The rule is true __________ all cases.
Don't worry; the guide will tell you how to avoid __________ ill while travelling.