单项选择题

Naturally, in a group of animals as diverse as the snakes, and with so many varied enemies, there are numerous defensive reactions and devices. There is, however, one general pattern of behavior. In the presence of suspected enemy the first reaction is to try to escape observation; if this fails, the next resort is the flight to some inaccessible retreat, but if this is not possible, or is circumvented, various kinds of intimidatory gestures and warning devices are brought into play; in the last resort the snake attacks. This pattern varies with the circumstances; some stages may be omitted or combined unpredictably whilst; some notoriously irascible species may dispense with all the preliminaries and attack almost at once, though seldom or never without some provocation.
Amongst the factors that increase aggressiveness are hunger, the mating season and surprise, with the last mentioned the commonest; when hunting for food or for mate, activity and the aggressive instinct are both at their peak. Owing to their poor sense of heating snakes are very liable to be, quite literally, caught napping and a similar situation arises during their periods of temporary blindness just before sloughing (蜕皮) begins. By far the greatest number of snake-bit accidents result from the unwitting disturbance of resting snakes, and this hazard is much increased with species that are well disguised and whose natural instinct is to trust to this concealment as their principal defense. As well as differences in aggressiveness between individuals of the same species according to the circumstances and conditions, there are also notable differences between species, even closely allied species; and the reports of those who have been attacked may understandably be lacking in objectivity. So it is impossible to forecast, even in outline, how any encounter will develop.
The Hamadryad, for example, is usually credited with being amongst the most aggressive of snakes, and there are many accounts of unprovoked attacks, yet on one occasion fourteen men and seven dogs passed and returned within two yards from a nest and no snake was seen although the female, which guards the nest, could not have been far away.
The author uses the example in the last paragraph to support his idea that

A. snakes do not begin the aggressive act if it is not disturbed.
B. some snakes are more aggressive and more ready to attack.
C. it is hard to forecast whether and how snakes would attack.
D. snakes often conceal themselves as their principal defense.

<上一题目录下一题>

热门试题

单项选择题

We can draw the conclusion from Paragraph 3 that the popularity of mobile televisions______.

A. is spurred by the popularity of soap operas
B. is welcome by young people of many countries
C. has something to do with the living condition
D. has resulted from the advancement of high-tech

单项选择题

In the United States today ______.A. alcoholism is not a major social problemB. there are no more than a million alcoholicsC. the problem of alcoholism costs thousands of millions of dollars every yearD. alcoholism has caused a million automobile accidents a year

Alcoholism is a major social problem in countries throughout the world. The United States is no exception. Experts believe that several million Americans are alcoholics today. Their health care needs, car accidents, reduced job performance and other problems cost thousands of millions of dollars every year.
In the early 1900s, many Americans joined in a campaign to make alcohol illegal in the United States. In 1920 an a mendment was added to the Constitution. It made drinking or selling alcohol a crime. But the new law did not stop people from drinking. Criminals produced or imported alcohol illegally and sold it almost everywhere.After a few years Americans realized the so-called Prohibition Law did not work. So in 1933 another constitutional change was made, canceling the amendment that made alcohol illegal.
In recent years Americans have taken other steps to deal with the problem of alcohol. One important action had been to increase the punishment for people who drive their automobiles after drinking alcohol. Many states now consider this to be a serious crime. Another important step has been to explain to children and students the dangers of alcohol. Many schools now offer special programmes to teach young people about the problem. Doctors have been working to develop new drugs and treatment programmes to help alcoholics. Finally, alcoholics themselves are dealing with the problem of alcoholism. Many of them have" gone on the wagon" and stopped drinking. They have joined the Alcoholics Anonymous group meeting regularly to discuss their problems and give each other support. "Going on the wagon" is not the only way to conquer alcoholism, but most alcoholic say it is the best way. They must give up alcohol completely so their own body and spirit can survive.