题目内容：

    Learning a second language is tricky at any age (and it only gets tougher the longer you wait to open that dusty French book). Now, in a new study, scientists have pinpointed the exact age at which your chances of reading fluency in a second language seems to plummet: 10.

The study, published in the journal Cognition, found that it’s “nearly impossible” for language learners to reach native - level fluency if they start learning a second tongue after 10. But that doesn’t seem to be because language skills go downhill. “It turns out you’re still learning fast. It’s just that you run out of time, because your ability to learn starts dropping at around 17 or 18 years old,” says study co-author Joshua Hartshorne, an assistant professor of psychology at Boston College.

Kids may be better than adults at learning new languages for many reasons. Children’s brains are more plastic than those of adults, meaning they’re better able to adapt and respond to new information. “All learning involves the brain changing,” Hartshorne says, “and children’s brains seem to be a lot more skilled at changing.”

Kids may also be more willing to try new things (and to potentially look foolish in the process) than adults are. Their comparatively new grasp on their native tongue may also be advantageous. Unlike adults, who tend to default（默认）to the rules and patterns of their first language, kids may be able to approach a new one with a blank slate（石板）.

These findings may seems discouraging, but it was heartening for scientists to learn that the critical period for fluent language acquisition might be longer than they previously thought. Some scientists believed that the brief window closes shortly after birth, while others stretched it only to early adolescence. Compared to those estimates, 17 or 18 -- when language learning ability starts to drop off -- seems relatively old. “People fared better when thy learned by immersion（沉浸）, rather than simply in a classroom. And moving to a place where our desired language is spoken is the best way to learn as an adult. If that’s not an option, you can mimic  an  immersive  environment  by  finding  ways  to  have  conversations  with  native  speakers  in  their own communities,” Hartshorne says. By doing so, it’s possible to become conversationally proficient -- even without the advantage of a child’s brain.

1.The word “plummet” in paragraph 1 is closest in meaning to “____”.

A.plunge B.rise C.end D.vary

2.What can be inferred from Joshua Hartshorne’s words?

A.Age 10 -18 is the best time to learn a second language.

B.Children are too young to grasp a second language.

C.Communicating with native speakers enables you to master all the language skills.

D.Adults go beyond the critical period for learning a second language.

3.What might be the reason why adults can’t reach native - level fluency in a second language?

A.Adults are less influenced by their mother tongues

B.Adults are only too willing to experience something awkward in the process.

C.Adults spend more time responding to new information.

D.Adults prefer an immersive environment to a classroom in learning a second language.

4.The passage is mainly about____.

A.the approaches to learning a second language

B.the best age to learn a second language.

C.why kids learn a second language more easily than adults

D.whether adults can learn a second language like their younger selves