A、They possess a high motivation. B、They are better language learners. C、They already know more than one language. D、They apply

M: How different would you imagine the learning of a second language to be, comparing older and younger learners? When might changes in learning style begin to take place?
W: One of the pieces of evidence that most strongly argues against the existence of a critical period for the acquisition of a second language suggests that there is no particular age when the ability to learn a second language declines. A critical period would be associated with a rather sharp fall-off in speed, ease, or success of second-language acquisition, but no such decline has ever been reported. Furthermore, studies that have compared the errors of older and younger learners who learn in similar contexts have found they make very similar errors, suggesting again that (6)they are applying quite similar cognitive processes to the learning challenge.
M: Do you have any possible explanations for the achievement of adults who demonstrate exceptionally strong abilities to learn a second language?
W: (7)Studies of highly successful adult second-language learners suggest that they have a high motivation to learn the target language, and (8)a period, typically early in the acquisition process, of full immersion in the target language, with minimal recourse to the first language. Of course, it is more often children who learn second languages that find themselves in this position of being highly motivated and left to sink-or-swim in the second-language setting. Consequently, it is perhaps not surprising that they are somewhat more likely to achieve high second-language proficiency.
M: What influences in second-language learning would you say are repeatedly overlooked by the researchers who conclude that children demonstrate a greater capacity to learn a second language than adults do?
W: (9)The missing variable in research on age differences in second-language acquisition is first language maintenance. Child second-language learners are somewhat more likely to achieve native-like proficiency in the second language than adult learners, and massively more likely to lose proficiency in their first language in the process. (10)Adult second-language learners almost never become monolingual in the process of learning a second language, as children often do. Thus, they master the greater cognitive and linguistic challenge of maintaining two languages, often at a very high level, with much greater success than children do.
M: Well, thank you Professor Snow.
W: My pleasure.
6．What do the similar errors of both older and younger learners show?
7．What accounts for the achievement of highly successful adult learners?
8．What does success in learning a target language involve?
9．What influences are repeatedly overlooked by researchers?
10．Why do adult second-language learners master greater cognitive and linguistic challenges?