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根据以下内容回答题：Social customs and ways of behaving change．Things which were considered impolite many years ago are now acceptable．Just a few years ago，it was considered impolite behavior for a man to smoke on street．No man who thought of himself by smoking when a lady was in a room．
Customs also differ from country to country．Does a man walk on the left or the right of a woman in your country?Or doesn’t it matter?Should you use both hands when you are eating?
Should leave one in your lap，or on the table?
The Americans and the British not only speak the same language but also share a large number of social customs．For example，in both America and England people shake hands when they meet each other for the first time．Als0．most Englishmen will open a door for a woman or offer their seat to a woman，and SO will most Americans．Promptness is important both in England and in America．That is，if a dinner invitation is for 7 o'clock，the dinner guest either arrives close to that time or calls up to explain his delay．
The important thing to remember about social customs is not to do anything that might make other people feel uncomfortable--especially if they are your guests．When the food was served，one of the guests started to eat his meats with a knife．The other guests were amused or shocked，but the host calmly picked up his knife and began eating in the same way．It would have been bad manners to make his guest feel foolish or uncomfortable．
If one has accepted a dinner invitation，what should he do if he is to be late for the dinner? A．He should find an excuse．
B．He should ask for excuse．
C．He should say sorry．
D．He should telephone to explain his being late．
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