单选题 What is the discussion mainly about?
  • A. The food web in the Pacific Ocean
  • B. The life cycle of the Pacific salmon
  • C. The consequences of overfishing
  • D. The importance of preserving salmon habitat
【正确答案】 B
【答案解析】[解析] 1-6 W1: Various species of Pacific salmon make a round trip from the small streams where they hatch, to the sea, and then back to the stream of their origin, where they spawn and die. This round trip is known as the salmon's run. The end of the salmon's run is the beginning of the next generation. Pacific salmon hatch in the headwaters of a stream. As fry, the fish then migrate downstream via rivers, and eventually to the ocean, where they require several years to mature. While in the sea, salmon from many river systems school and feed together. When mature, the salmon form into groups of common geographic origin and migrate back toward the river they emerged from as juveniles. M: Is it true that they find their way home by their sense of smell? W1: During the first stage of their return, they navigate by the position of the sun. But later, when they reach the fiver leading to their home stream, their keen sense of smell takes over. M: Just what is it that they can smell? The other fish? W1: The water flowing from each stream carries a unique scent. This scent comes from the types of plants, soil, and other components of that stream. This scent is apparently imprinted in the memory of a salmon fry before it migrates to the sea. W2: I had a real shock when I was hiking once. I was looking at a waterfall, and I saw a salmon jump up, about ten feet! At first, I couldn't believe my eyes. But then I saw another one do it! And then several more! It was an awesome sight. M: They must have an incredibly powerful instinct. W1: The survival of their species depends on their ability to get home and reproduce. And, of course, other species depend on the survival of the salmon. Salmon provide an important link in the food web. They spend 90 percent of their lives in the ocean, where they feed on plankton, shrimp, and small fish. When they make their return journey, they carry nutrients from the ocean back to the rivers and streams. M: I used to live near a river, and the eagles would gather for the salmon run every year. They'd gorge themselves on all the salmon that had just spawned. W1: Nothing is wasted in nature. After the salmon spawn, their carcasses feed birds, mammals, and vegetation--and even their own newly hatched offspring. 1. What is the discussion mainly about? The professor says: Various species of Pacific salmon make a round trip from the small streams where they hatch, to the sea, and then back to the stream of their origin, where they spawn and die; Pacific salmon hatch...; As fry...; When mature
单选题 What does the professor mean when she says this:
  • A. Reproduction is the goal of the salmon's run.
  • B. Salmon can swim very fast to escape predators.
  • C. Future generations of salmon will face habitat loss.
  • D. Salmon migrate great distances in search of food.
【正确答案】 A
【答案解析】[解析] What does the professor mean when she says this: "This round trip is known as the salmon's run. The end of the salmon's run is the beginning of the next generation." The professor means that reproduction is the goal of the salmon's run. The salmon's run ends with the beginning of the next generation, when young salmon hatch.
多选题 According to the discussion, how do salmon find their way to their home stream? Click on 2 answers. By following other fish By seeing the sun's position By listening for waterfalls
【正确答案】 B、D
【答案解析】[解析] According to the discussion, how do salmon find their way to their home stream? Salmon find their way home by seeing the sun's position: ... they navigate by the position of the sun. They also smell the water: ...their keen sense of smell takes over; The water flowing from each stream carries a unique scent.
单选题 Listen again to part of the discussion. Then answer the question.
Why does the student say this:
  • A. She saw one large fish eat many smaller fish.
  • B. She felt sick after seeing dead fish in the river.
  • C. The sight of leaping salmon amazed her.
  • D. There were more salmon than she could count.
【正确答案】 C
【答案解析】[解析] Listen again to part of the discussion. Then answer the question. "I had a real shock when I was hiking once. I was looking at a waterfall, and I saw a salmon jump up, about ten feet! At first, I couldn't believe my eyes. But then I saw another one do it! And then several more! It was an awesome sight." Why does the student say this: "At first, I couldn't believe my eyes." The sight of leaping salmon amazed the student. She was surprised to see a fish jump up a waterfall, and then she was amazed to see several others also jump.
单选题 According to the discussion, why are salmon an important link in the food chain?
  • A. They eat small fish that make other animals sick.
  • B. They move vegetation downstream to the sea.
  • C. They produce more eggs than they need.
  • D. They carry nutrients from the ocean to streams.
【正确答案】 D
【答案解析】[解析] According to the discussion, why are salmon an important link in the food chain? The professor says: Salmon provide an important link in the food web; When they make their return journey, they carry nutrients from the ocean back to the rivers and streams.
单选题 What can be concluded from this statement:
  • A. Baby salmon eat the bodies of dead salmon.
  • B. everal natural food sources are endangered.
  • C. Salmon eat a variety of other life forms.
  • D. An adult salmon reproduces several times.
【正确答案】 A
【答案解析】[解析] What can he concluded from this statement: "Nothing is wasted in nature. After the salmon spawn, their carcasses feed birds, mammals, and vegetation--and even their own newly hatched offspring." You can conclude that baby salmon eat the bodies of dead salmon. After salmon spawn, they die. Their dead bodies, or carcasses, become the food source for many organisms, including newly hatched baby salmon.