阅读短文，根据要求完成下面各小题。
Think of life as a game in which you are playing with five balls in the air．You name them work，family，health，friends and spirit（精神）and you keep all of them in the air．You will soon understand that work is a rubber ball．If you drop it，it will bounce（弹跳）back．
But the other four balls，family，health，friends and spirit，are made of glasses．If you drop one of these，they will be broken．They will never be the same．You must understand that and try to have balance in your life．How?
Don't look down on your worth by comparing yourself with others．It is because we are different and each of us is special．
Don't let other people set goals for you．Only you know what is best for yourself．
Don't give up when you still have something to give．（3）Nothing is really over until the moment you stop trying．
Don't be afraid to fight difficulties．It is by taking chances that we learn how to be brave．
Don't shut love out of your life by saying it's impossible．（4）The quickest wav to receive love is to give it；the fastest way to lose love is to hold it too tightly（紧紧地）；the best way to keep love is to give it wings．
Don't run through life so fast that you forget not only where you’ve been，but also where you are going．
Don't be afraid to learn．Knowledge is weightless．It's a treasure（珍宝）you can always carry easily．
Don't use time or words carelessly．You can't get them back．
Life is not a competition，but a trip，step by step．
Yesterday is history，tomorrow is a mystery（秘密），and today is a gift：that's why we call it “the present”．
A．根据短文内容简要回答问题。
1．What are the five balls of life?
2．Please say something about knowledge according to the passage．
B．将短文中划线的两个句子译成汉语。
3．
4．
C．请给短文拟一个适当的标题。
5．