阅读理解Passage 1 　　Manners evolved differently in different cultures. In earlier times there was a tendency for manners to become increasingly formal, and this was often viewed as progress. In the 18th and 19th centuries having good manners was seen as an important part of one’s education and social class, and it was necessary to be taken as a lady or a gentleman to get ahead in the world.　　In the 20th and 21st centuries, manners have gradually become more relaxed and informal. The hosting of dinners and other social gatherings are no longer the exclusive privilege of the wealthy elite (精英), and private clubs are being gradually replaced by more open meeting places. So the manners of the salon (沙龙) are gradually combining with the manners of the pub. Clothing is a good indication of the changes in manners, as can be seen in the following examples.　　It is surprising that the wearing of hats indoors by males is once again becoming acceptable. Students in North America often wear baseball caps to class. In many countries the wearing of hats indoors by males was once acceptable even in very polite society, but over the years this became considered as a lower-class behavior and was thus discouraged in both the middle and upper classes. The young people who wear hats indoors do not realize they are actually restarting a very old cultural tradition.　　A comparable development for females is the wearing of jeans. Many females now wear jeans on a daily basis, either at home or at work. Some see this as a symbolic declaration that they are now modern women, not girls or ladies. Some girls, like boys, wear baseball caps both indoors and outdoors.　　Sneakers and shorts are now acceptable for either males or females in a variety of non-athletic situations. Some companies have rules requiring informal dress such as jeans or sneakers on Fridays (called “dress-down Friday” or “casual Friday”), and others permit it almost all the time. In these companies, and many others, it is acceptable to call the bosses by their first names.1What does the passage mainly talk about?