Questions 15 to 21 are based on the following passage.
While the body is remarkably symmetrical in many ways, in some key areas, it's decidedly one-sided. About 10 percent of people are left-handed, a proportion that has remained relatively stable.
People who study the brain have a number of theories about what drives handedness, but are at a loss to explain why humans are the only species with handedness. One theory holds that hand dominance is established in the womb by the hand that babies prefer to hold to their mouths, while another says higher testosterone in the womb can increase the chances of becoming a lefty.
But regardless of what sets the pattern, handedness can play a role in how we think, behave and interact with others. The brain, after all, is asymmetrical, with many thinking and intellectual skills centered in the left hemisphere, while emotional and mood-related functions are concentrated in the right. Some studies, for example, find that left-handed people tend to be more vulnerable to negative emotions such as depression and anger, possibly because southpaws, as they're known, engage the right sides of their brains more actively.
Scientists have also found that lefties may be more prone to fear than righties, and therefore may be vulnerable to post-traumatic stress disorder. Clearly, these associations aren't absolute — otherwise, no left-handers would ever jump out of a plane or brave New York City streets as a taxi driver. But scientists have found that left-handers have more symmetry between the right and left sides of their brains compared with right-handers. And that can have implications for everything from language to motor skills.
"The majority of people who are right-handed are left-hemisphere language dominant," says Dr. Daniel Geschwind, a professor of neurology at the University of California, Los Angeles. That means most of their language processing occurs in the left side of the brain. "Almost 10 percent of left-handers have that flipped, and have right-hemisphere language dominance, and many have almost equal distribution of language skills in both hemispheres," Geschwind says. "The notion is that left-handers are less constrained when it comes to brain asymmetry, so their skills are most randomised and less specified" to one side of 30 the brain or the other.
That can have advantages, particularly after a stroke. Right-handed patients who have a stroke on the left side of the brain tend to recover their speaking abilities more slowly than left-handers, since they don't have the wider distribution of language networks throughout both sides of the brain. But there's also a reason why left-handedness isn't more common, even if it provides such advantages. "Having more distributed language abilities probably makes the system more complicated, so it may increase the susceptibility to developmental abnormalities and neurodevelopmental disorders," says Geschwind. That could explain some studies that correlated risk of autism with being left-handed.
Appreciating how that lack of symmetry translates into benefits or risks is still a work in progress. In the meantime, lefties should celebrate their differences — or, in the case of their brains, the lack of difference between their right and left sides.
Questions:
15 The writer begins the passage with
A. a surprising fact
B. a statistical evidence
C. a shocking discovery
16 Paragraph 2 is mainly about
A. theories that explain handedness
B. reasons why humans are the only species with handedness
C. the link between higher testosterone level and left-handedness
17 The word sets (line 9) can be replaced by
A. distinguishes
B. determines
C. monitors
18 Left-handed people tend to
A. cope with stress better
B. be good at languages
C. be more emotional
19 — otherwise no left-handers would ever jump out of a plane or brave New York City streets as a taxi driver (lines 18 and 19). This comment supports the idea that
A. lefties can overcome their fear
B. not all lefties are prone to fear
C. lefties are as fearless as righties
20 flipped (line 27) means
A. mixed
B. reversed
C. changed
21 The main idea of paragraph 6 is
A. the advantages of left-handedness
B. the benefits and risks of being a left-hander
C. the link between stroke, speaking ability and handedness
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