From Mr. Ward Hoffman. Sir, I was halfway through Professor Raj Persaud's article “What's the tipping point'(Financial Times Weekend, April 9-l0) when it occurred to me that what I was reading was not ironic(讽刺的). If Prof Persaud wants to know why Americans tip in restaurants, he need only ask the first American he meets in London. Americans tip in restaurants for one reason, and one reason only: we tip to supplement (补贴) the salary of restaurant workers. Quality of service does not enter into it, beyond the fact that one may tip a bit less for poor service, or a little more for good service. Not tipping at all in a non-fast-food restaurant is not a choice. In the US, one used to tip about 15 per cent for dining in a family-style restaurant or in an upmarket (高档的) restaurant. Here, in San Francisco Bay area restaurants, we are encouraged to tip 20 per cent or more, to help restaurant workers live in this very expensive area. After eating at an Italian restaurant in my city, I left a tip of 20 per cent on the non-tax part of our dinner bill. It was expected. There is nothing more complicated (复杂的) than that about Americans tipping in restaurants. Ward Hoffman, Palo Alto, CA 94306, US *                *                  * From Mr. Philip McBride Johnson. Sir, I agree with most of Raj Persaud's opinions about the doubtful value of tipping, but with one exception(例外). Tips can be very useful when one is a repeat customer or diner. It is only when the tipper is a stranger and likely to remain so that the system does not work to his or her advantage. But frequent a hotel or a restaurant, always tip a bit more, and the difference in service and treatment will be easily felt. Philip McBride Johnson, Great Falls, VA 22066, US 68. What can we learn from Hoffman's letter? A. Quality of service determines tipping in the US. B. Americans don't tip in non-fast-food restaurants. C. Tipping in US upmarket restaurants is unnecessary. D. How to tip in the United States is not complicated. 69. Johnson's letter shows ________. A. a stranger in a restaurant is likely to tip a bit more B. diners receive better service if they frequent a restaurant C. repeat diners may get good service if they tip a bit more D. the tipping system works to the advantage of new customers 70. From the two letters, we can learn Professor Raj Persaud ______ . A. feels doubtful about the value of tipping B. believes tipping improves quality of service C. wants to ask Hoffman about tipping in the US D. thinks tipping a bit more one can get good service 71. The two letters most probably appears in a ______. A. notice               B. handbook            C. book review        D. newspaper