16．Scientists studied works of art made at various times in history and found most of the people shown in these works of art are right-handed.So scientists guessed that right-handedness has always been common in humans through history.Because no one has ever come across records of any large groups of left-handed nations or people，scientists also guessed that right-handedness is a natural characteristic（特征）of humans.Today，only about 10 to 15 percent of the world's population is left-handed.
Scientists now know that a person's two hands each have every special job.For most people，the left hand is used to find things，hold things，or support things.The right hand is used to handle or work with things.This division of work seems to be related to how the two sides of the brain work.The right side of the brain，which controls the left hand，is strong in skills related to making a person's hands and eyes work together.The left side of the brain，which controls the right hand，is the center for thinking and solving problems.Studies have found that left-handedness is twice as common among artists as among people in other jobs.
What makes a person become right-handed rather than left-handed？So far，no one really knows for sure.Scientists have found that almost 40 percent of the people who suffer major brain damage when they are born become left-handed.However，not everyone who suffers brain damage becomes left-handed，so scientists guess that there must be another reason.One simple idea suggests that people normally get right-handedness from their parents.If a person does not receive the gene（基因）for right-handedness，he/she may become either right-handed or left-handed according to chance and the person's surroundings.
Even though right-handedness is more common，the left-handed are no longer looked down on，nor are they considered abnormal（反常的）.Left-handed children used to be punished until they began using their right hands like other children，but today either case is perfectly acceptable.
（1）Which fact supports the idea that right-handedness is a natural characteristic？
A．Scientists found the right-handed gene.
B．Right-handed people are cleverer.
C．Most famous people were right-handed.
D．No large left-handed groups of people exist in the world.
（2）The second paragraph describes
.
A．the two hands separately
B．problems that left-handed people have
C．the connection of the brain to the hands
D．how a person becomes left-handed
（3）People sometimes become left-handed because
.
A．it is accepted
B．the left hand is more artistic
C．their brain is damaged
D．right-handed children are punished
（4）Suppose the world's population is 6.5 billion，how many left-handed people are there？
A．About 2 billion.
B．About 1 billion.
C．About 500 million.
D．About 100 million.
