阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空。

    Someone  ( say), "Time is money."

    But I think time is much  important than money. Why? when money is spent, we can get it back later. However,  time is gone, it'll never return. That is why we must not  time.

    It goes with saying that time is usually limited(有限的). Even a second is very important. We should make full use of our time to do something  (use).But it is a pity that there are a lot of people who do not know the  (important) of time. They spend their limited time  (smoke), drinking and playing. They do not know that wasting time means wasting part of their own lives.

    In a word. we should  time. We shouldn't leave  (today) work for tomorrow. Remember we must save time.