单项选择题

Passage Two
Born without sight, 7-year-old Lucas Murray used to be so afraid of walking that he wouldn’t take a step without his parents. He wouldn’t walk on a bumpy surface.
But now, Lucas has become more mobile than his parents ever imagined, running with friends, playing basketball and jumping on a trampoline (蹦床)—all on his own.
The incredible change is owed to a technique called echolocation, similar to the method used by dolphins and bats, that allows Lucas to paint a picture of his surroundings using the sound he creates himself.
To "see" the world around him, he dicks his tongue and listens to the echo that bounces back. From the sound, he can make out the location, depth and shape of objects around him, allowing him to navigate (导航) even unfamiliar areas.
Though it’s estimated that only about 5% to 10% of the blind population now uses a sonar (声呐系 统)-type approach, the Murrays hope it could someday become as common as the cane.
Two years ago, Daniel Kish, a blind psychologist who has practiced the technique since childhood and has been teaching it for more than 15 years, traveled to the Murrays’ hometown and worked with Lucas for four days, teaching him not just echolocation, but also convincing Lucas and his parents that blindness doesfft need to be a limiting condition.
"You have to let go, and it’s the hardest thing in the world;’ said Sarah Murray. When Kish suggested the family let Lucas walk along the shore on his own, she said, "It was frightening. And Lucas found it frightening too:"
But after the family overcame the initial fear, Lucas made rapid progress.
He learned how to detect different-sized bowls and cardboard panels by clicking to navigating grocery stores entirely on his own. In addition to clicking, Lucas also uses a white cane to find his way.
"He likes exploring things, and he likes climbing things" his mother said. "He’ll go up the elevator. That wouldn’t have been believable in a million years:’ She said the technique is second nature to him now.

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