Niagara Fall is a great tourist ________, drawing millions of visitors every year.
At the meeting they discussed different ______ to the study of mathematics.
.The children were warned of not being too _______ about things you are not supposed to know.
It was difficult to guess what her _____ to the news would be.
Having been attacked by terrorists,________.
We must know what we should do and what we should avoid ______a good impression on others in public place.