根据以下资料，回答12~15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 behaviour for a man to smoke on the street．No man who thought of himself as being a gentleman would make a fool of himself by smoking when a lady was in a room.

Customs are also different 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? What about table manner? Should you use both hands when you are eating?

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．Also, 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．There is an old story about a man who gave a dinner party．When the food was served, one of the guests started to eat his peas 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.

"Bad manners" in the last sentence means __.