Our brains work in complex and strange ways．There are some people who can calculate the day of the week for any given date in 40,000 years, but who cannot add two plus two．Others can perform complex classical piano pieces after hearing them once, but they cannot read or write．
Dr．J．Langdon Down first described this condition in 1887．He called these people idiot savants．An idiot savant is a person who has significant mental impairment （损伤） , such as in autism ( 孤独症，自闭症) or retardation．At the same time, the person also exhibits some extraordinary skills, which are unusual for most people．The skills of the savant may vary from being exceptionally gifted in music or in mathematics, or having a photographic memory．
One of the first descriptions of a human who could calculate quickly was written in 1789 by Dr．Benjamin Rush, an American doctor．His patient, Thomas Fuller, was brought to Virginia as a slave in1724．It took Thomas only 90 seconds to work out that a man who has lived 70 years, 17 days, and 12 hours has lived 2,210,500,800 seconds．Despite this ability, he died in 1790 without ever learning to read or write．
Another idiot savant slave became famous as a pianist in the 1860s．Blind Tom had a vocabulary of only 100 words, but he played 5 ,000 musical pieces beautifully．
In the excellent movie Rain Man, made in 1988 and available on video cassette, Dustin Hoffman plays an idiot savant who amazes his brother played by Tom Cruise, with his ability to perform complex calculations very rapidly．
Today we more clearly recognize that the idiot savant is special because of brain impairment．Yet not all brain impairment leads to savant skills．Some studies have shown that people who have purposeful interruption of the left side of the brain can develop idiot savant skills．However few people wish to participate in such experiments．There are many excellent reasons for not undergoing unnecessary experimentation on one's brain．The term idiot savant is outdated and inappropriate．Virtually all savants have a high degree of intelligence and are thus not idiots．
What does the passage mainly talk about?

A．Idiot savants have areas of outstanding abilities．

B．Human Beings have complicated thinking process．

C．The brains of the idiot savants are partly impaired．

D．The reasons why people have wonderful skills vary．

Which of the following can be done by Rain Man?

A．He can play wonderful pieces of classical music．

B．He can guess out exactly the length of a man's life．

C．He can memorize the contents of the pictures fast．

D．He can count matches dropped on the floor quickly．

What can you infer from the passage?

A．Idiot savants have real talents for art and math．

B．Dr．Down is the first person who found idiot savants．

C．Few people wish to risk becoming savants by brain operations．

D．Intentional left brain impairments will surely lead to idiot savants．

Which of the following shows the structure of the passage?