选择答案：正确错误查看解析

Insects´ lives are very short and they have many enemies, but they must survive long enough to breed and perpetuate their kind. The less insect like they look, the better their chance of survival. To look “inedible” by resembling or imitating plants, is a deception widely practiced by insects. Mammals rarely use this type of camouflage, but many fishes and invertebrates do.

The stick caterpillar is well named. It is hardly distinguishable from a brown or green twig. This caterpillar is quite common and can be found almost anywhere in North America. It is also called “measuring worm” of “inchworm”. It walks by arching its body, then stretching out and grasping the branch with its front feet, then looping its body again to bring the hind feet forward. When danger threatens, the stick caterpillar stretches its body away from the branch at an angle and remains rigid and still, like a twig, until the danger has passed.

Walkingsticks, or stick insects, do not have to assume a rigid, twiglike pose to find protection, they look like inedible twigs in any position. There are many kinds of walkingsticks, ranging in size from the few inches of the North American variety to some tropical species that may be over a foot long. When at rest their front legs are stretched out. Some of the tropical species are adorned with spines or ridges, imitating the thorny bushes or trees in which they live.

Leaves also seem to be a favorite object for insects to imitate. Many butter flies can suddenly disappear from view by folding their wings and sitting quietly among the foliage that they resemble.

1. What is the main subject of the passage?

A. Catepillars that live in trees

B. The feeding habits of insects

C. How some insects camouflage themselves

D. Insects that are threatened with extinction

2. In lines 1, the word “enemies” refers to.

A. other creatures competing for space

B. extreme weather conditions

C. creatures that eat insects

D. inedible insects

3. According to the passage, how does the stick caterpillar make itself look like a twig?

A. By holding its body stiff and motionless

B. By looping itself around a stick

C. By changing the color of its skin

D. By laying its body flat against a branch

4. Which of the following is true of stick insects?

A. They resemble their surroundings all the time.

B. They make themselves look like other insects.

C. They are camouflaged only when walking.

D. They change color to make themselves invisible.

5. Which of the following are not mentioned in the passage as objects that are imitated as a means of protection?

A. Thorns B. Flowers C. Leaves D. Sticks

6.In which paragraph does the author describe the way in which stick caterpillars move?

A. Paragraph one B. Paragraph two

C. Paragraph three D. Paragraph four

查看解析

选择答案：正确错误查看解析

选择答案：正确错误查看解析

No casual observer of a lichen would ever suspect that it was a composite of interacting life forms. The seemingly uncomplicated lichen is actually composed of a fungus and a colony of algae (or blue-green algae, which some scientists now consider to be bacteria). A few species even include all three of these diverse forms of life. A complete lichen is strikingly different from its separated partners in both appearance and biochemistry; many produce unique compounds which cannot be made by the component organisms alone.

Lichens grow in almost every natural habitat imaginable, from deserts to tropical rain forests—even on the back of certain beetles in New Guinea and inside rocks(along with algae) in the otherwise barren dry valleys of Antarctica.

Many species can not tolerate extreme heat, cold or dryness. Very few, however, can survive heavy air pollution, and many live only where the air is very clean. The disappearance of lichens from an area gives warning of a threatened environment.

1. Which of the following would be the best title for the passage?

A. The versatility and complexity of the lowly lichen

B. The hidden characteristics of algae colonies

C. The disappearance of the lichen species

D. The habitats of spectacular fungi

2. The author states that lichens grow “as though designed to be ignored” because they are

A. not totally understood by botanists

B. troublesome to collect for the purposes of study

C. uncomplicated in their internal structure

D. not easily noticed by observers

3. According to the author, most people are unaware that lichen is a.

A. leafy plant

B. class of simple bacteria

C. two-dimensional life form

D. Combination of organisms

4. The “unique” compounds mentioned in the second paragraph are produced.

A. through the cooperative efforts of the lichen’s parts

B. only under laboratory conditions

C. through one of the three possible processes

D. once in the lichen’s life cycle

5. The author implies that lichens might be used to.

A. find water sources

B. destroy unwanted plant life

C. test for air purity

D. provide food in remote areas

查看解析