题目

If English means endless new words, difficult grammar and sometimes strange pronunciation, you are wrong. Haven’t you noticed that you have become smarter since you started to learn a language?According to a new study by a British university, learning a second language can lead to an increase in your brain power. Researchers found that learning other languages changes grey matter. This is the area of the brain which processes information. It is similar to the way that exercise builds muscles. The study also found the effects are greater, the younger people learn a second language.A team led 如图，用十字形方框从日历表中框出5个数，已知这5个数的和为5a-5，a是方框①，②，③，④中的一个数，则数a所在的方框是（　　）A. B. C. D.