The teacher made____ her duty to care for the lives and study of her students.
We can no longer ____to consider water an almost free resource that we can use as much as we like.
After talking with his father for about half an hour, he felt better and began to know how to ____ this kind of situation.
---I failed today’s math test! What shall I do?---____! Try once more.
He lost his job three years ago; _____, he was seriously injured in an accident last week.
Of all the subjects, I like ____ history best because it gives us ____ useful knowledge of things in the past.