The most obvious difference between the working class and the middle class in English is thek ______ .

A．are extremely small in number so that media pays no attention to them
B．still uses old words like "sir" in everyday life
C．includes the hereditary aristocracy
D．refers only to the royal family

A．Because it sounds too servile and is likely to cause embarrassment.
B．Because it can only be used in certain occupations.
C．Because it is an impolite word.
D．Because it shows that the speaker is not a well-bred person.