2--Yes,that is why I never drink it.
 
1--Do you drink green tea,then?
 
2--Very seldom, because tea has tannin which may be harmful to one's health.
 
1--But if the tea is good and well prepared,it will do much good.
 
2--What is it good for?
 
1--Not only can it appease one's thirst,but it can also refresh one when tired.
 
2--That's true,but it must not be allowed to stand long.
 
1--Why is it so?
 
2--Because if you drink a kind of tea which has been prepared for some time before,it will do you harm.
 
===================================
注解：
 
1.seldom很少
2.well prepared准备充分的  
3.appease one's thirst止渴
 
===================================
译文：
 
1--张先生，你不喜欢喝红茶吗？
2--是的，所以我永不喝它的。
1--那么你喝绿茶吗？
2--很少的，因为茶里有单宁酸，对人的健康是有害的。
1--但是好的茶叶，泡得又好，是很有益处的呢。
2--有什么益处？
1--茶不但能够止渴，又能使疲惫的人提起精神来。
2--那是对的，但是不可以让它搁得太久。
1--为什么呢？
2--因为如果你喝一种放得太久的茶，是没有好处的。