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  3. The unknown pervades the universe. That which people can see, with the aid of various sorts of telescope, accounts for just 4% o

The unknown pervades the universe. That which people can see, with the aid of various sorts of telescope, accounts for just 4% o

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问题     The unknown pervades the universe. That which people can see, with the aid of various sorts of telescope, accounts for just 4% of the total mass. The rest, however, must exist. Without it, galaxies would not survive and the universe would not be gently expanding, as witnessed by astronomers. What exactly constitutes this dark matter and dark energy remains mysterious, but physicists have recently uncovered some more clues, about the former, at least.
    One possible explanation for dark matter is a group of subatomic particles called neutrinos. Neutrinos are thought to be the most abundant particles in the universe. According to the Standard Model, the most successful description of particle physics to date, neutrinos come in three varieties, called "flavors". Again, according to the Standard Model, they are point-like, electrically neutral and massless. But in recent years, this view has been challenged, as physicists realized that neutrinos might have mass.
    The first strong evidence came in 1998, when researchers at an experiment, based in Japan, showed that muon neutrinos produced by cosmic rays hitting the upper atmosphere had gone missing by the time they should have reached an underground detector. Its operators suspect that the missing muon neutrinos had changed flavor, becoming electron neutrinos or-more likely-tau neutrinos. Theo- ry suggests that this process, called oscillation, can happen only if neutrinos have mass.
    Over the coming months and years, researchers hope to produce the most accurate measurements yet. The researchers created a beam of muon neutrinos first. On the other side of the target sat a particle detector that monitored the number of muon neutrinos leaving. The neutrinos then travelled 750km (450 miles) through the Earth to a detector in a former iron mine in Soudan, Minnesota. Researchers then were able to confirm that a significant number of muon neutrinos had disappeared-that is, they had changed flavor. While their mass is so small that neutrinos cannot be the sole constituent of dark matter, they have an advantage in that they are at least known to exist.
    The same cannot be said for sure of another possible form of dark matter being studied by a group of physicists in Italy. If the result continues to withstand scrutiny, it would appear to be evidence for an exotic new sort of fundamental particle, known as an axion, which could also be a type of dark matter.
What aspect about neutrinos has been questioned in recent years?
选项 A、Neutrinos are in the shape of points.
B、There are altogether three different varieties of Neutrinos.
C、Neutrinos do not have any mass.
D、Neutrinos are the most abundant particles in the universe.
答案C
解析 细节题；题干中的定位关键词是neutrinos，由于是本篇中的专有名词，比较容易帮助我们定位本题考查的区域，在原文中相关信息出现在第二自然段。而考查词则是question，比较原文我们可以看出这里的question对应于原文的challenge，这个词之前提到的 point-1ike和massless，以及B和D选项的内容在原段落中都有体现，但是当我们再比较阅读challenge之后的内容，我们发现that neutrinos might．have mass确定了这个题目的正确选项针对是neutrinos是否有mass的问题，mass在这里是“质量，重量”的意思。
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