现用18O作为示踪原子进行如下反应：2SO2（g）+18O2（g） 2 SO3（

British people are far more sophisticated about beverages than they were 50 years ago. Witness the Starbucks revolution and you’ll know where (1) goes. However, spurred on by recent studies suggesting that it can cut the risk of (2) and retard the aging process, tea is enjoying a (3) .

Although tea is available in more places than ever, it remains to be (4) of a typical British family.

If you are invited to an English home, (5) in the morning you get a cup of tea. It is either brought in by a heartily (6) or an almost malevolently silent maid. When you are (7) in your sweetest morning sleep you must not say: "Go away, you (8) ." On the contrary, you have to declare with your best five o’clock smile. "Thank you very much. I (9) a cup of tea, especially in the morning." If they leave you alone with the liquid you may pour it (10) !

Then you have (11) ; then you have tea at 11 o’clock in the morning; (12) ; then you have tea for tea; then after supper; and again at eleven o’clock (13) .

You must not refuse any additional cups of tea under the(14) if it is hot; if it is cold; if you are (15) ; if you are nervous; if you are watching TV; (16) ; if you have just returned home; if you feel like it; if you do not feel like it; if you have had no tea (17) ; if you have just had a cup.

You definitely must not (18) . I sleep at five o’clock in the morning; I have coffee for breakfast; I drink innumerable (19) during the day; I have the (20) even at tea-time!

3（）

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