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