Learning a second language can improve brain power, scientists believe. US researchers from Northwestern University say bilingualism  is a form of brain training -- a mental "work out" that adjusts the mind finely. Speaking two languages well affects the brain and changes how the nervous system reacts to sound, lab tests showed. Experts say the experiment performed by the National Academy of Sciences provides "biological" evidence of this. In an attempt to prove the guess that speaking two languages is good for one's mind, the team monitored how the brain of 48 healthy student volunteers reacted to different sounds. Twenty three of these volunteers were bilingual. The scientists used special equipment to trace the pattern of brainwaves. Under quiet, laboratory conditions, the bilingual students responded in a similar way to the English-only-speaking students, who formed the control group. But the bilingual group were far superior at processing sounds even when there were a lot of people talking in the room. They were better able to focus on to the important information -- the speaker's voice -- and block out other _ noises. Prof Nina Kraus, who led the research, said: "The bilingual's better experience with sound results in a hearing system that is highly efficient, flexible and focused in its automatic sound processing, especially in challenging or novel listening conditions." Co-author Viorica Marian said: "People do crossword puzzles and other activities to keep their minds sharp. But the advantages we've discovered in double language speakers come automatically simply from knowing and using two languages.'' Musicians appear to gain a similar benefit when rehearsing , say the researchers. According to some theories, being bilingual might help avoid dementia . How was the bilingual group better at processing sounds?
They were the control group. They could better fix their attention on something of importance. They were able to find the speaker's voice quickly. They had better nervous system.
Question: Learning a second language can improve brain power, scientists believe. US researchers from Northwestern University say bilingualism  is a form of brain training -- a mental "work out" that adjusts the mind finely. Speaking two languages well affects the brain and changes how the nervous system reacts to sound, lab tests showed. Experts say the experiment performed by the National Academy of Sciences provides "biological" evidence of this. In an attempt to prove the guess that speaking two languages is good for one's mind, the team monitored how the brain of 48 healthy student volunteers reacted to different sounds. Twenty three of these volunteers were bilingual. The scientists used special equipment to trace the pattern of brainwaves. Under quiet, laboratory conditions, the bilingual students responded in a similar way to the English-only-speaking students, who formed the control group. But the bilingual group were far superior at processing sounds even when there were a lot of people talking in the room. They were better able to focus on to the important information -- the speaker's voice -- and block out other _ noises. Prof Nina Kraus, who led the research, said: "The bilingual's better experience with sound results in a hearing system that is highly efficient, flexible and focused in its automatic sound processing, especially in challenging or novel listening conditions." Co-author Viorica Marian said: "People do crossword puzzles and other activities to keep their minds sharp. But the advantages we've discovered in double language speakers come automatically simply from knowing and using two languages.'' Musicians appear to gain a similar benefit when rehearsing , say the researchers. According to some theories, being bilingual might help avoid dementia . How was the bilingual group better at processing sounds?
A. They were the control group.
B. They could better fix their attention on something of importance.
C. They were able to find the speaker's voice quickly.
D. They had better nervous system.
Answer: