Visitors to Britain may find the best place to sample local culture is in a traditional pub. But these friendly hostelries can be minefields of potential gaffes for the uninitiated.
An anthropologist and a team of researchers have (1) some of the arcane rituals of British pubs—starting with the (2) of getting a drink. Most pubs have no waiters—you (3) to go to the bar to buy drinks. A group of Italian youths (4) for 45 minutes before they realized they would have to (5) for their own. This may sound inconvenient, but there is a (6) purpose.
Pub culture is designed to (7) sociability in a society known for its reserve. Standing at the (8) for service allows you to chat with others (9) to be served. The bar counter is possibly the only (10) in the British Isles in which friendly conversation with (11) is considered entirely appropriate and really quite normal (12) . "If you haven’t been to a pub, you (13) been to Britain." This tip can be found in a (14) , Passport to the Pub: The Tourists’ Guide to Pub Etiquette, a (15) code of conduct for those wanting to sample "a central part of (16) life and culture". The trouble is that if you do not (17) the local rules, the experience may fall flat. For (18) , if you are in a big group, it is best if only one (19) two people go to buy the drinks. Nothing irritates the (20) customers and bar staff more than a gang of strangers blocking all access to the bar while they chat and dither about what to order.

平面图形中的各线段，可分为三种：（）。

A.已知线段

B.中间线段

C.连接线段

D.独立线段