Ⅰ.阅读理解
Three divers enter a hole leading to a waterfilled cave on Mexico's Yucatan Peninsula. They swim for an hour. Finally, they reach a large room 60 feet underground and about the size of two basketball courts. Here, they discover an upsidedown human skull. Other bones lie nearby.
The team came across the skull in 2007. The divers then told the Mexican government about the finding. Soon the government formed a team of scientists to look into it. The group, which included archaeologist Dominique Rissolo, believed that the skull belonged to someone who lived in the last ice age. At the ice age some twenty thousand years ago, sea levels dropped and new land appeared. Over time, rain and wind ate holes into some of the land.
“The person may have died after entering the cave，” Rissolo says. Then, when the ice age ended some ten thousand years ago, sea levels rose. Water flooded the cave, covering the remains.
Worrying that moving the skull might destroy it, scientists decided to examine it at its watery resting place. They collected information about the skull and other pieces of bones. They found that the bones belonged to a 15 to 17yearold girl who lived at least twelve thousand years ago. The team named her after a type of water nymph (仙女) in Greek myths: the Naiads (Naia)．
Naia is the oldest nearly complete human skeleton (骨架) ever found in the Americas. DNA tests showed that she's a direct ancestor of presentday Native Americans. Naia's DNA also matches with people native to Siberia, a part of Russia. Scientists have long thought that ancient people from this area arrived in Alaska during the last ice age. They were the first humans to live in the Americas. And Naia proves how far south they went.
In 2014 the scientists decided to bring up Naia's skull from the cave to protect it from curious divers. So it was taken to a lab, where it remains today.
文章大意：本文是一篇说明文。三名潜水者在位于墨西哥的尤卡坦半岛的一个洞穴里发现了一个头骨。这掀起了一场考古行动。
1. What can we learn about the skull?
A．It was left alone in the cave.
B．It lay under a basketball court.
C．It drew the government's attention.
D．It was discovered by three scientists.
答案：C
解析：推理判断题。由文章第二段第一句至第三句可知，潜水者发现了头骨之后，将这一发现报告给了墨西哥政府。不久之后，政府派遣了一个由科学家组成的小组去调查这个发现。由此可以推知，这一发现引起了政府的关注。故选C。
2. Why was the skull studied in the cave?
A．Scientists tried to protect it.
B．The temperature was fine there.
C．It was against the law to take it out.
D．It would help scientists study the cave.
答案：A
解析：细节理解题。由文章第四段第一句“Worrying that moving the skull might destroy it, scientists decided to examine it at its watery resting place”可知，科学家们担心移动这个头骨会破坏它，所以他们就在发现它的地方研究它。所以，科学家们在山洞里研究头骨是为了保护头骨。故选A。
3. Who were Naia's distant ancestors?
A．Early humans in Greece.
B．Early humans in Siberia.
C．Early humans in Alaska.
D．Early humans in Mexico.
答案：B
解析：推理判断题。由文章第五段中的“Naia's DNA also matches with people native to Siberia...they went”可知，Naia的DNA还和西伯利亚原住民的DNA相吻合。科学家们认为来自西伯利亚的古人们在最后一个冰河世纪到达了阿拉斯加。他们是最早生活在美洲的人。Naia证明了他们向南迁移了多远。由此可知，Naia的远祖是西伯利亚的原住民。故选B。
