You might not normally think of frogs as being colorful, but these frogs definitely are—the dart-poison frogs of Central and South America. They have striking colors—often yellow with black stripes or deep blue with black spots.
Beyond being nice to look at, these markings have a purpose. They warn predators that these frogs are poisonous. When threatened, these frogs secrete a substance through their skin that would easily kill whatever animal might try to eat them. Their bright colors communicate this, and so most animals tend not to hunt them.
Now, speaking of hunting, for centuries these frogs were sought after by hunters. As you might think, the hunters didn’t want to eat the frogs, but rather, they captured them for their poison. They would add the poison to the tips of their hunting arrows—of course, nowadays most hunters use guns.
These days dart-poison frogs are of less interest to hunters than to medical researchers. Researchers believe that they can make new heart medicine from the poison, because it acts as a stimulant on the body’s nervous system. Researchers think they would use it to stimulate a weak heart.
There is, however, a problem with doing research on these frogs. Those that are caught in the wild will produce their poison until they die. However, those that are born in captivity will not produce any poison at all.
（10分）
(1)What is the passage mainly about?（2分）
AThe characteristics of dart-poison frogs.
BThe habitat of dart-poison fogs.
CThe role of dart-poison frogs in their ecosystem.
DThe various ways dart-poison frogs can camouflage themselves.
正确答案A您的答案是 D回答错误展开
(2)What does the speaker imply about the frogs’ colors?（2分）
AThey don’t vary within the species.
BThey change when the frog is threatened.
CThey attract the frogs’ mates.
DThey help protect the frogs
正确答案D您的答案是 B回答错误展开
(3)What did hunters use to do with the frogs that they captured?（2分）
AThey ate them.
BThey used their skins to make dyes.
CThey collected the frogs’ poison.
DThey used them to make medicine.
正确答案C您的答案是 A回答错误展开
(4)What is the problem with frogs born in captivity?（2分）
AThey die shortly after birth.
BThey don’t produce any poison.
CTheir behavior is too unpredictable.
DThey don’t develop the colorful markings.
正确答案B您的答案是 D回答错误展开
(5)Why are scientists studying dart-poison frogs?（2分）
ATo develop new drug therapies.
BTo learn how to reverse the effects of their poison.
CTo discover how to breed them successfully in captivity.
DTo help repopulate the species.
正确答案A您的答案是 C回答错误
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