[speaker001:] Do you object to drinking black tea, Mr.Zhang?
[speaker002:] Yes, that is why I never drink it.
[speaker001:] Do you drink green tea, then?
[speaker002:] Very seldom, because tea has tannin which may be harmful to one's health.
[speaker001:] But if the tea is good and well prepared, it will do much good.
[speaker002:] What good is it for?
[speaker001:] Not only can it appease one's thirst, but it can also refresh one when tired.
[speaker002:] That's true, but it must not be allowed to stand long.
[speaker001:] Why is it so?
[speaker002:] Because if you drink a kind of tea which has been prepared for some time before, it will do you harm.