Nowadays more and more people are beginning to be aware of the seriousness of ______________.
It is only during the last years that man has become generally aware that ______________.
There is an old saying, ______________. It’s the experience of our forefathers, however, it is correct in many cases ever today.
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The English proverb says, ______________. This is quite true because ______________.
______________ is now______________, and at the same time ______________. These two factors have caused ______________. Then what shall we do to solve ______________ in the face of such a situation.
One of our ancient philosophers said, ______________. Chinese people have always been holding this idea to be one of their standards of morality.
One of the great early writers said that ______________. If this is true, the present situation should make us ponder over ______________.