A、No reason can explain why some people are left-handed. B、Difference in gender and nationality is the concerned factor. C、The c

Why are some people left-handed? Scientists have been trying to answer that question for many years. Research has shown that ninety percent of people naturally use their right hands for most tasks. But hundreds of millions of people use their left hands. (26)A study done in 1992 found that men are more likely to be left-handed than women. It also found that Asian or Hispanic people are less likely to be left-handed than white people, black people or North American Indians. Some cultures accept people who do things mostly with their left hands. Others do not．(27)For example, in some countries eating with left hand is considered as an insult to others． is the genetic theory. It says that people right-or-left-handed because of genes passed to them by their parents．
(28)Amar Klar at the National Cancer Institute believes right-handed people are born with a gene for it. About twenty percent of people do not have the right-handed gene. These people could be either left-handed or right ability as well as extremely high intelligence. They say a great number of left-handed people were famous political leaders, artists, scientists or athletes.