The adderis the only poisonous snake nativeto 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 far 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 far 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 some pepe very ill, there are probably just as many cases of bites having little or no effect, as there are of serious illness.
What does the underlined phrase “ trodden on” probably mean?

A．Found out

B．Heard from

C．Stepped on.

D．Robbed of.

Where are adders to be found?

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

What should you do if you are with someone who is bitten by an adder?

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.

What’s the best title of the passage?

A．Poisonous Snakes	B．Adders in Britain
C．Take Care oif Sake Bites	D．Protec Endangered Adders