单选题 Being smart is the most expensive thing we do. Not in terms of money, but in a currency that is vital to all living things: energy. One study found that newborn humans spend close to 90 percent of their calories on building and running their brains. (Even as adults, our brains consume as much as a quarter of our energy.) If, during childhood, when the brain is being built, some unexpected energy cost comes along, the brain will suffer. Infectious disease is a factor that may rob large amounts of energy away from a developing brain. A great deal of research has shown that average IQ varies around the world, both across nations and within them.
Higher IQ predicts a wide range of important factors, including better grades in school, a higher level of education, better health, better job performance, higher wages, and reduced risk of obesity. So having a better understanding of variations in intelligence might yield a greater understanding of these other issues as well.
In a study in 2010, it was found that, among all the factors that affect intelligence, infectious disease works as the best predictor of the bunch. A recent study by Christopher Hassall and Thomas Sherratt repeated the study using more sophisticated statistical methods, and concluded that infectious disease may be the only really important predictor of average national IQ.
Support for this hypothesis comes not only from cross-national studies, but from studies of individuals. There have been many studies, for example, showing that children infected with intestinal worms have lower IQ later in life. Another study by Atheendar Venkataramani found that regions in Mexico that were the target of malaria eradication programs had higher average IQ than those that were not. In practical terms, however, this means that human intelligence is mutable. If differences in IQ across the world are largely due to exposure to infectious disease during childhood, then reducing exposure to disease should increase IQ.
Despite the strength of the findings, the study was not without its limitations. The researchers did their best to control for the effects of education. But what they really needed was to repeat their analysis across regions within a single nation, preferably one with standardized, compulsory education. The nation they chose was the United States. Average IQ varies in the states. Again, infectious disease was an excellent predictor of average state IQ. The states with the five lowest average IQ all have higher levels of infectious disease than the states with the five highest average IQ, and the relationship was good across all of the states in between.
So far, the evidence suggests that infectious disease is a primary cause of the global variation in human intelligence. Since this is a developmental cause, rather than a genetic one, it's good news for anyone who is interested in reducing global inequality associated with IQ. It will allow people interested in using this information to raise the IQ of people around the world to target their efforts most effectively and efficiently.

单选题 We can learn from the first paragraph that
A. energy is the most important factor that affects intelligence.
B. newborn babies spend more calories than adults in running their brains.
C. extra energy cost may cause intellectual damage to children.
D. there are IQ variations among and within nations.

单选题 Higher average IQ in one place may
A. explain why people there can get a better understanding.
B. indicate the possibility of having an infectious disease.
C. show the history of less infectious diseases there.
D. show that people there are slimmer than those with lower IQ.

【正确答案】 C

【答案解析】[解析] 细节题。根据题干higher average IQ定位在第二、三段。第二段主要说明高智商对人的教育、健康等方面有影响。2010年研究表明，传染性疾病在所有影响智力的因素中具有最大的影响。接下来又指出，最近也有研究表明传染病也许是预测国民平均智商的唯一真正重要的因素。由此可推断出，传染性疾病影响智力的发展，一个地区智力平均水平高，则可以反过来说明该地区所经历的传染性疾病可能相对较少，故C项“表明那一地区较少的传染病史”正确。

单选题 The word "mutable" (Para. 4) is closest in meaning to
A. changeable. B. exchangeable.
C. acceptable. D. susceptible.

【正确答案】 A

【答案解析】[解析] 含义题。根据题干定位在第四段。第四句话In practical terms, however, this means that human intelligence is mutable(然而从实践的角度出发，这意味着人们的智商是______)，句中的this指代第二、三句的内容，这两句用两个研究分别从正反两方面指出传染病对智力的影响，第一个研究表明患过肠虫病的孩子智商比较低，第二个研究表明在实施过消除疟疾措施的地区，人们的智商更高。mutable后第五句是研究得出的结论：既然在很大程度上，智商的差异是由传染性疾病的情况决定的，那么减少传染病就可能提高智商。由此可以推出，人的智商是可以通过减少传染病来提高，即人类的智商是可以改变的，故A项“可以改变的”为正确答案。

单选题 Which of the following is true according to Paragraphs 4 and 5?
A. Children with higher IQ may have suffered from intestinal worms.
B. Malaria affects most Mexicans' physical health.
C. Average IQ variation in the U.S. is not so obvious.
D. Education is also a factor that affects intelligence.

【正确答案】 D

【答案解析】[解析] 细节题。根据题干定位到第四、五段。这两段对研究的结论以及过程进行了详细的介绍，第五段第一句指出，尽管研究结论非常具有说服力，但研究仍然有局限性。接着第二、三句具体指出：研究人员尽全力控制教育因素对研究结果产生的影响，实施标准化义务教育的国家会更适合成为研究的对象，也就是说要将教育者这一因素变成一个常量，才能够准确得知传染病对智商的影响，故可推断出D项“教育也是影响人智商的一个因素”正确。