If you have always suspected that you might just be a mosquito magnet(磁铁), scientists now have evidence for you: Mosquitoes indeed are attracted to certain humans more than others, according to a new study. 

A research team led by Leslie Vosshall, a professor at Rockefeller University, sought to identify why certain people seem to draw more mosquitoes than others. The research findings were published in the journal Cell on October 18.

Over the course of three years, researchers asked a group of 64 volunteers to wear nylon stockings on their arms for six hours a day over multiple days. Maria Elena De Obaldia, the study’s first author, constructed a “two-choice olfactometer assay(嗅觉计测定)”—an acrylic(丙烯酸的) glass room in which researchers put two of the stockings. The study team then released yellow fever mosquitoes into the room and observed which stocking drew more insects.

This test allowed researchers to separate study participants into “mosquito magnets”, whose stockings drew lots of mosquitoes, and “low attractors”, who didn’t seem as attractive to the insects. The scientists examined the skin of the mosquito magnets carefully and found 50 molecular compounds(分子化合物) that were higher in these participants than the others.

“We had no idea about what we would find,” Vosshall, who is also chief scientific officer of the Howard Hughes Medical Institute, said. But one difference was particularly distinctive: The mosquito magnets had much higher rates of carboxylic acid(羧酸) on their skin than the low attractors. Carboxylic acids are found in sebum(皮脂), the oily substance that creates a barrier and helps keep our skin moisturized(滋润). The carboxylic acids are large molecules, Vosshall explained. They’re “not that smelly by themselves”, she said. But beneficial bacteria on the skin “chew on these acids, that produces the characteristic smell of humans”—which may be what attracts mosquitoes, according to Vosshall.

1.What can we know about the research?

A The 64 volunteers wore stockings all day.

B It was conducted at Rockefeller University.

C The first author is Leslie Vosshall.

D It lasted for three years.

解析：选D。D细节理解题。根据第三段第一句的“Over the course of three years”可知该研究持续了三年。故选D。

2.Why did researchers separate the participants into two groups?

A To indicate a conclusion.

B To introduce a topic.

C To give an explanation.

D To make a comparison.

解析：选D。D推理判断题。根据第三段最后一句的“...observed which stocking drew more insects”和第四、五段的对比可知，研究人员将参与者分成两个组（“mosquito magnets”和“low attractors”）主要是为了把他们进行对比。故选D。

3.What does Vosshall think makes “mosquito magnets” more attractive to mosquitoes?

A Beneficial bacteria.

B An oily substance.

C Some large molecules.

D Sebum in the skin.

解析：选C。C细节理解题。根据最后一段的“The mosquito magnets had much higher rates of carboxylic acid(羧酸) on their skin than the low attractors.”和“The carboxylic acids are large molecules”以及最后一句“beneficial bacteria on the skin ‘chew on these acids, that produces the characteristic smell of humans’”可知，吸蚊者皮肤上的羧酸（一种大分子）含量比低吸引者高得多，皮肤里的有益菌咀嚼羧酸产出人体独特的气味，从而吸引了蚊子。故选C。

4.From which is the text probably taken?

A A biology textbook.

B A health magazine.

C A research paper.

D A travel brochure.

解析：选C。C推理判断题。根据全文可知，文章围绕一个关于“为什么蚊子偏爱某些人群”的研究展开，最有可能在研究报告里出现。故选C。