以上4张卡片均为一面是图案，另一面是阿拉伯数字。现在断定：如果一面是梅花，那么另一面是6。如果要检验该断定正确与否，且只允许翻动以上两张卡片，正确的选择是（）
A．翻动第一张和第三张
B．翻动第二张和第三张
C．翻动第一张和第四张
D．翻动第二张和第四张
参考答案：D
解析：
题目给定的条件是：卡片的一面是图案，一面是阿拉伯数字。题目给定的推断：如果一面是梅花，那么另一面是6。这是一个充分条件假言命题。如果前件真而后件假，则该充分条件假言命题才是假的。即只有在图案面是梅花，而数字面不是6时，该命题为假，其余情况为真。因此只需翻动第二张和第四张卡片，就可以判断题干推断的真假。故选D。
| 完形填空 | |||
| Time spent in bookshops can be most enjoyable,whether you are a book-lover or merely you are thereto buy a book as a present. You may even have entered the shop just to find shelter from a 1_ . Whatever the reason, you can soon become totally __2_ your surroundings. The desire to _3_ a book with attractive" dust-jack" (封面 ) is irresistible (不可抵抗的) although this method of selection ought not to be __4__ ,as you might end up with a rather __5__book. You soon become absorbed in some book or _6_ ,and usually it is only much later that you realize you have spent far too much time __7_ , and must dash off to keep some forgotten appointments without buying a book, __8__ . This opportunity to escape the realit es of everyday life is,l think,the main __9 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 _10 such places to your heart's content. If it is a good shop, __11_assistant will approach you with inevitable (必不可少的) greeting : " Can I help you , sir?" You needn't buy anything you don't want. In a bookshop an assistant _12_ remain in the background until you have finished browsing. Then,and 13 ,are his services necessary. Of course you may want to find out where a particular section is,but when he or she has led you there ,the assistant should _ 14 carefully and look as if he or she is not interested in selling a __15_ book. You have to be careful not to be attracted by variety of books in a bookshop. It is very __16 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 __17_vaguely (含糊的 ) interested you up until then. This volume on the subject,however, __18_ 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. _ 19_ running up a huge account,you can __20_a great deal of time wandering from section to section. | |||
| ( )1. A. terrible accident ( )2. A. unaware of ( )3. A. take out ( )4. A. learned ( )5. A. interesting ( )6. A. the other ( )7. A. there ( )8. A. anyhow ( )9. A. purpose ( )10. A. walk in ( )11. A. no ( )12. A. mustn't ( )13. A. only then ( )14. A. go out ( )15. A. dear ( )16. A. easy ( )17. A. not ( )18. A. was supposed to ( )19. A. Apart from ( )20. A. spend | B. sudden shower B. interested in B. pick out B. followed B. dull B. others B. here B. however B. fun B. step into B. an B. shouldn't B. then B. retire B. cheap B. usual B. already B. happened to B. Instead of B. have | C. short rain C. absorbed in C. take away C. taken C. handsome C. another C. reading C. of course C. reason C. wander round C. the C. should C. at this time C. disappear C. useless C. hard C. hardly C. appeared to C. Because of C. waste | D. heavy traffic D. satisfied with D. pick up D. given D. regretful D. other D. writing D. though D. attraction D. listen in D. some D. can't D. at no time D. help D. single D. attractive D. only D. occurred to D. Except for D. enjoy |