[单项选择]

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. But the desire to pick up a book with an attractive dust-jacket is irresistible. You soon become absorbed in some book or other, and usually it is only much later that you realize that you have spent far too much time there.
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 the 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
A. as soon as you have entered the shop
B. just before you finish browsing
C. only when you have finished reading
D. when he leads you to a particular section

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. But the desire to pick up a book with an attractive dust-jacket is irresistible. You soon become absorbed in some book or other, and usually it is only much later that you realize that you have spent far too much time there.
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 the 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
A. the dust-jackets are very attractive
B. you start reading one of the books
C. it is raining outside
D. you have to make sure you don’t buy a dull book as a present