Time spent in a bookshop can be most enjoyable, whether you are a book-lover or merely there to buy a book as a present. You may even have entered the shop just to find shelter from a sudden shower. Whatever the reason, you can soon become totally unaware of your surroundings. The desire to pick up a book with an attractive dust-jacket is irresistible, although this method of selection ought not to be followed, as you might end up with a rather dull book. You soon become engrossed in some book or other, and usually it is only much later that you realize you have spent far too much time there and must dash off to keep some forgotten appointment--without buying a book, of course.This opportunity to escape the realities of everyday life is, I think, the main attraction of a bookshop. There are not many places where it is possible to do this. A music shop is very much like a bookshop. You can wander round such places to your heart’s content. If it is a good shop, no assistant will approach you with inevitable greeting: "Can I help you, sir" You needn’t buy anything you don’t want. In a bookshop an assistant should remain in the background until you have finished browsing, then, and only then, are his services necessary. Of course you may want to find out where a particular section is, but when he has led you there, the assistant should retire carefully and look as if he is not interested in selling a single book.You have to be careful not to be attracted by the variety of books in a bookshop. It is very easy to enter the shop looking for a book on ancient coins and to come out carrying a copy of the latest best-selling novel and perhaps a book about brass-rubbing something that had only vaguely interested you up until then. This volume on the subject, however, happened to be so well illustrated and the part of the text you read proved so interesting that you just had to buy it. This sort of thing can be very dangerous. Apart from running up a huge account, you can waste a great deal of time wandering from section to section. "Dust-jacket" in the first paragraph probably means ().

A. a kind of clothes
B. protecting paper cover of a book
C. book cover full of dust
D. the title of a book