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  3. How sharks navigate the vast and seemingly featureless ocean has long been a

How sharks navigate the vast and seemingly featureless ocean has long been a

游客2024-01-14  60
问题     How sharks navigate the vast and seemingly featureless ocean has long been a mystery. Now there’s evidence they may follow their noses. Sharks rely on their sense of smell to help chart a path through the ever-shifting waters of the deep seas, according to a new study. Scientists have supposed that the animals navigate by monitoring smell clues or the Earth’s magnetic field, but no one knew for sure.
    In new experiments near San Diego, scientists ferried wild leopard sharks about 6 miles (10 kilometers) away from their preferred habitats, fitted them with tracking devices, and stuffed some of the animals’ noses with cotton balls. "Just 30 minutes after being released facing the wrong way, sharks with full use of their smells made a corrective U-turn and then headed straight back to shore, " says study leader Andrew Nosal, a researcher at the Scripps Institution of Oceanography, California.
    Sharks with stuffed noses, meanwhile, "appeared lost", wandering aimlessly and swimming more slowly than those that could smell freely. To test sharks’ sense of direction, Nosal and colleagues captured several dozen leopard sharks, a small species found along the coast from Washington State to northern Mexico.
    After blocking some of the animals’ noses, the scientists then took the animals on a cruise to deeper waters before slipping them, safe and unharmed, back into the sea. Even the sharks with plugged noses made it partway back to shore before their tracking devices fell off. But those with unplugged noses "took very straight paths" toward home. Nosal supposes the sharks likely sniffed out chemical molecules found in higher and higher doses nearer to land.
    Other scientists, however, remain unconvinced. Maybe the animals with plugged noses "were confused by the fact that they had something stuffed in their nose," says Kim Holland, a marine biologist at the University of Hawaii at Manoa. It’s also unlikely the animals were following a smell that grew stronger closer to land, adds Jayne Gardiner, a sensory biologist at the New College of Florida. Animals that couldn’t smell a thing still turned toward the beach, which "suggests something else is really guiding them", she says.
    Study leader Nosal responds that sharks with cotton-stuffed nose willingly eat, suggesting that a congested nose doesn’t upset them much. He agrees that sharks use a variety of markers to find their way, "but the point is that smell participates in navigation, " he says, "Our study was only the first step in solving this mystery. " [br] We can infer from the passage that________.
选项 A、there are various markers for sharks to find their way and eyes play an important role in it
B、some scientists hold different opinions from the findings of the new study
C、the new study has completely solved the mystery of sharks’ easy navigation in the vast ocean
D、the sharks likely sniffed out chemical molecules found in higher doses nearer to land
答案 B
解析 根据文中第五段第一句“Other scientists, however, remain unconvinced. ”可知，一些科学家对这项新研究的发现持有不同的观点，故选B。
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