20．The adder is the only poisonous snake native to Britain．Adders have the most highly developed poison injecting mechanism of all snakes，but they are not aggressive animals．Adders will only use their poison as a last means of defence，usually if caught or trodden on．No one has died from adder bites in Britain for over 20 years．By faar the most common smake in Britain is the adder．In Scotland，in fact，there are no other snakes at all．The adder is also the only British sanke with a poisonous bite．It can be found almost anywhere，but prefers sunny hillsides and rough open country，including high gournd．In Ireland there are no snakes at all．
Most people regard snake bites as a fatal misfortune，but not all bites are serious，and very few are fatal．Sometimes attempts at emergency treatment turn out to be more dangerous than the bite itself，with amateurs heroically，but mistakenly，trying do-it-yourself surgery and other unnecessary measures．
All snakes have small teeth，so it follows tha tall snakes can bite，but only te bite of the adder presents any danger．British snakes are shy animals and are fare more frightened of you than you could possibly be of them．The adder will attack only if it feels threatened，as can happen if you take it by surprise and step on it accidentally，or if you try to catch it or pick it up，which it dislikes intensely．If it hears you coming，it will normally get out of the way as quickly as it can，but adders cannot move very rapidly and may attack before moving if you are very close．
The effect of a bite varies considerably．It depends upon severa things，one of which is the boidy-wight of the person bitten．The bigger the person，the less harmful the bite is likely to be，which is why children suffer far more seriously from snake bites in Britain，and thought these bites can make soime pepe very ill，thre are probaably just as many cases of bites having little or no effect，as there are of serious illess．
28．What does the underlined phrase"trodden on"probably mean？C
A．Found out B．Heard from C．Stepped on D．Robbed of．
29．Where are adders to be found？B
A．In fertile fields in Scotland
B．On wild land throughout Britain．
C．In many parts of Britain and Ireland
D．Everywhere in Britian except Scotland
30．What should you do if you are with someone who is bitten by an adder？C
A．Catch the biting adder at onece
B．Don't worry about the bitten person．
C．Don't try to treat the bite by yourself
D．Operate on the person as soon as possible．
31．What's the best title of the passage？B
A．Poisonous Snakes
B．Adders in Britain
C．Take Care oif Sake Bites
D．Protec Endangered Adders．
分析 文章主要介绍了 adders 这种蛇，包括它的分布、习性、以及被蛇咬时应注意的事项等．
解答 CBC B
28：C 推断题．由划线词所在句"Adders will only use their poison as a last means of defence，usually if caught or trodden on．"可知，adders 不到万不得已不会使用毒液，这种万不得已的情况通常是被捉到或被 trodden on 的时候．A项"找出"，B项"听说"，C项"踩上"，D项"抢劫"，只有C项代入文章能讲得通，即 adders 在被捉到或被踩到的时候才会使用毒液．其他三项均不符合语境，故正确答案为C．
29 B 细节题．由第一段倒数第二句"It can be found almost anywhere，but prefers sunny hillsides and rough open country，including high ground．"可知，adders 几乎在任何地方都能被找到，尤其喜欢阳光充足的山坡和贫瘠广袤的乡村，包括高地．即在 Britain 的野地里可以找到 adders，所以B项正确．A项，由第一段倒数第二句"…prefers sunny hillsides and rough open country …"可知，adders 喜欢贫瘠的地方而非肥沃的地方，所以A项错误．C项，由第一段最后一句"In Ireland there are no snakes at all．"可知C项错误．D项，由第一段倒数第四句"Scotland，in fact，there are no other snakes at all．"可知，Scotland 只有 adders 这一种蛇类，所以D项错误．故正确答案为B．
30：C 细节题．由第二段第二句"Sometimes attempts at emergency treatment turn out to be more dangerous than the bite itself，with amateurs heroically，but mistakenly，trying do-it-yourself surgery and other unnecessary measures．"可知，遇到有人被蛇咬，慌忙地处理是很危险的，也千万不要试着自己处理，故正确答案为C．
31：B 主旨题．文章主要介绍了 adders 这种蛇，包括它的分布、习性、以及被蛇咬时应注意的事项等．adders 为本文关键词，贯穿整篇文章，所以B项正确．A项，毒蛇有很多种，本文只介绍 adders 这一种，所以A项错误．C项，处理蛇咬伤口，偏离文章主旨，所以C项错误．D项，保护濒危蛇类，偏离文章主旨，所以D项错误．故正确答案为B．
点评 考察学生的细节理解和推理判断能力，做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确的选择．在做推理判断题不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
