Comprehension 理解
Answer these questions:
1 Why does the author find it odd that snakes should be capable of manufacturing poison?
2 What is the difference between neurotoxic and haemolytic poison?
Vocabulary 词汇
Refer to the text to see how the following words have been used, then write sentences of your own using these words: mild (1.1); converted (1.2); defies analysis (1.2); the survival competition (1.3); carnivore (1.7); a twoedged weapon (11.7-8); concocted (1.9); extreme potency (1.9); viperine (1.19).
The paragraph 段落
A Drawing your information from the first paragraph (lines 1-9), write a list of points in note form to answer the following question: Why is the author justified in stating that Nature behaved in an unpredictable way in allowing snakes to manufacture poison?
B Read the last paragraph again (lines 13-19)．Then, using the list of points given below, reconstruct the paragraph in your own words as far as possible．Do not refer to the passage until you have finished the exercise.
1 Nerve poison (e.g．mambas): neurotoxic．
2 Blood poison (e.g．vipers): haemolytic．
3 Blood poison the more unpleasant.
4 Nerve poison possibly the more primitive.
5 Blood poison a later development.
6 But nerve poison acts more quickly on man.
7 Purpose of poison: not against man, but snake's prey: e.g．rats.
C Write a paragraph of about 200 words on one of the following subjects:
1 Our fear of snakes.
2 The survival competition.
Key structures 关键句型
A Compare these two sentences:
Instead of saying: They had the ability to catch and live on prey without using poison if they wanted to (but they didn't).
We can say: They could have caught and lived on prey without using poison．(1.3)
Write sentences using the following expressions:
could have succeeded; could have stayed; could have bought.
B Write sentences using the following expressions:
force upon (11.2-3); live on (1.3); conversion into (1.10); different from (1.11); act on (1.12); effect on (1.19).
C Compare these two sentences:
Instead of saying: They could have caught and lived on prey without using poison, just as the thousands of nonpoisonous snakes still catch and live on prey without using poison.
We can say: They could have caught and lived on prey without using poison, just as the thousands of nonpoisonous snakes still do．(11.3-4)
Complete the following sentences by adding the correct form of do:
1 Even though he has retired, he still gets up early just as he always____.
2 He certainly enjoys music as much as you____.
3 If you act as he ____ you won't be very popular.
D Study the following sentence:
Both poisons are unpleasant, but by far the more unpleasant is the blood poison．(11.14-15)
Why is the more used here and not the most?
Write two sentences using the more and the most.
E Note how the word far has been added for emphasis in this sentence: Nerve poison does its business … far more quickly than … (1.17)
The word much may be used in the same way．We can say much more quickly, using much in an emphatic way.
Write sentences using the following phrases: much more expensive; far more difficult; far less exciting;much less interesting.
Special difficulties 难点
A Study the following pairs of words and then write sentences of your own to bring out the difference.
1 merely (1.4)----only
I'm not blaming you．I'm merely trying to find out how this happened．
Only the head of the department can authorize a withdrawal from a course.
2 fierce (1.6)----furious
You can see armed guards along the border accompanied by fierce dogs.
He was terribly annoyed．Indeed, he was furious!
3 take place (1.10)----take part
All these events took place before you were born.
How many of you are taking part in the play?
4 prey (1.3)----pray
The tiger seized its prey and tore it into pieces.
You've done your best．All you can do now is pray for success.
Explain the verbs in italics in the following:
How it came about that snakes manufacture poison is a mystery．(1.1)
I'm sorry I said that．I don't know what came over me.
He came up with some very interesting ideas.
I came across an old friend of yours while I was abroad．
C Write sentences using the following words and phrases: enable (1.4); running fights (1.6); in fact (1.7); in every respect (1.11); so to speak (1.16); be that as it may (11.16-17).
D Supply full stops and commas where necessary in the following paragraph．Do not refer to the passage until you have finished the exercise:
The makers of the nerve poison include the mambas and the cobras and their venom is called neurotoxic vipers (adders) and rattlesnakes manufacture the blood poison which is known as haemolytic both poisons are unpleasant but by far the more unpleasant is the blood poison it is said that the nerve poison is the more primitive of the two that the blood poison is so to speak a newer product from an improved formula be that as it may the nerve poison does its business with man far more quickly than the blood poison this however means nothing snakes did not acquire their poison for use against man but for use against prey such as rats and mice and the effects on these of viperine poison is almost immediate．(11.13-19)
Multiple choice questions 多项选择题
Choose the correct answers to the following questions.
Comprehension 理解
1 One of these statements is true．Which one?
a．Snakes need poison to digest their food．
b．Snakes can feed on other animals without the use of poison.
c．Non-poisonous snakes find survival more difficult than poisonous ones.
d．All snakes are capable of manufacturing poison.
2 The possession of poison in the saliva makes hunting ____.
a．easy for all carnivores
b．a two-edged weapon when carnivores fight each other
c．almost effortless for snakes
d．unpredictable, as Nature intended
3 The poison that acts on the blood ____.
a．acts less rapidly than nerve poison
b．doesn't affect the victim as badly as nerve poison
c．is made by snakes like mambas and cobras
d．was probably the first of the two kinds of poison to be developed
4 Human beings ____.
a．can't compare with prey such as rats and mice
b．respond to all snake poisons in the same way
c．are likely to survive nerve poison but not blood poison
d．are not the intended victims of snake poison
Structure 句型
5 They ____ have been able to catch and live on prey without using poison．(1.3)
a．might
b．should
c．would
d．must
6 They could have caught and lived on prey without ____ poison．(1.3)
a．to use
b．use
c．the use of
d．have used
7 For ____ snakes, poison is merely a luxury．(1.4)
a．these
b．a
c．-
d．an
8 Blood poison is the more unpleasant ____．(1.15)
a．of them all
b．of the two
c．in the world
d．among them both
Vocabulary 词汇
9 Saliva is a natural ____．(11.1-2)
a．oil in the body
b．snake-poison
c．digestive process
d．body fluid
10 Poison would be ____ to all carnivores．(1.7)
a．an asset
b．a help
c．a necessity
d．a disadvantage
11 Arsenic and strychnine ____ us in different ways．(1.11.11-12)
a．effect
b．result
c．affect
d．cause
12 The nerve poison is thought to be ____(11.15-16)
a．less highly developed
b．more potent
c．more recent
d．less complicated