B
If you go to the Gulf of Mexico, you can see there is a big hole. It is called Chicxulub Crater (希克苏鲁伯陨石坑). Some people believe it was because of a huge asteroid (小行星) hitting this place, and the hit made dinosaurs die out millions of years ago.
This idea was first suggested in 1980. Later, scientists used special tools to find out what would happen if it was true. It showed that the asteroid could hit Earth at 40,000 miles per hour, leading to a big hole, a great tsunami (海啸), earthquakes, and the melting (融化) of tons of rock. The hit took away millions of lives around the Chicxulub Crater.
The terrible story didn't stop there. Minutes later, hot rock started to rain down, and there was deadly dirt everywhere on the ground. Many animals were burnt to death. After several hours, a super-hot wind knocked down anything still standing.
In weeks, the sky was full of ash. Days became nights. This covered the sunlight for months or even years. Many plants died first. Then lots of animals died too because of food shortage, including almost all dinosaurs.
Although this idea sounds possible, the question of how dinosaurs died out remains unsolved scientifically. But as scientists discover more dinosaur fossils, we may know the truth one day.
( )6. What does the underlined word it in Paragraph 2 refer to?
A. The thought that the asteroid made dinosaurs die out.
B. The fact that Chicxulub Crater is in the Gulf of Mexico.
C. The truth that all dinosaurs died out millions of years ago.
D. The idea that a rock from space made a big hole on Earth.
( )7. According to the scientist, what happened when the asteroid hit Earth?
A. The hit made lots of rock melt.
B. Millions of lives were lost in Mexico.
C. A big hole appeared in North America.
D. The asteroid hit Earth at 40,000 miles per second.
( )8. According to the idea, what was the reason for the death of almost all dinosaurs?
A. Ash and dirt.
B. No sunlight.
C. Food shortage.
D. The asteroid's hit.
( )9. Which of the following statement is TRUE?
A. Hours later, animals died because of harmful gases.
B. We will surely know the truth from dinosaur fossils.
C. The dirt after the hit didn't hurt animals on the ground.
D. There isn't a scientific reason for the dinosaur's die-off.
( )10. Where can you probably find this passage?
A. In a storybook about dinosaurs.
B. In an encyclopaedia of animals.
C. In a science book about space.
D. In a travel magazine about Mexico.
答案：6.D
解析：第二段第一句提到 “这个观点（小行星撞击导致恐龙灭绝）于 1980 年首次被提出”，随后 “Later, scientists used special tools to find out what would happen if it was true”（之后，科学家用特殊工具研究若 “它” 为真会发生什么）。结合上下文，“it” 指代的是前文 “小行星撞击地球形成希克苏鲁伯陨石坑” 这一具体事件（即 “来自太空的岩石在地球上砸出大洞”），而非 “恐龙灭绝” 这一结果。A 选项侧重 “恐龙灭绝” 的结论，B、C 与上下文无关，故选 D。
7.A
解析：根据第二段“the asteroid could hit Earth at 40,000 miles per hour, leading to... the melting of tons of rock.”可知，撞击导致大量岩石融化，A选项正确。B选项“墨西哥失去数百万生命”文中是“around the Chicxulub Crater”，并非整个墨西哥；C选项“北美出现大洞”文中未提及地点是北美；D选项“每秒40,000英里”错误，是“每小时40,000英里”。
8.C
解析：根据第四段“Many plants died first. Then lots of animals died too because of food shortage, including almost all dinosaurs.”可知，恐龙灭绝的直接原因是食物短缺，C选项正确。A选项“火山灰和泥土”、B选项“没有阳光”是导致植物死亡的原因，进而导致食物短缺；D选项“小行星撞击”是最初原因，但不是恐龙死亡的直接原因。
9.D
解析：根据最后一段“the question of how dinosaurs died out remains unsolved scientifically.”可知，恐龙灭绝的原因在科学上尚未解决，即还没有科学的解释，D选项正确。A选项“几小时后动物因有害气体死亡”文中是“burnt to death”和“super-hot wind”；B选项“我们一定会从恐龙化石中知道真相”文中是“may know”，并非“surely”；C选项“撞击后的泥土没有伤害地面动物”与第三段“there was deadly dirt everywhere on the ground. Many animals were burnt to death.”矛盾。
10.A
解析：文章主要讨论恐龙灭绝的原因（小行星撞击理论），与恐龙相关，最可能出现在关于恐龙的故事书中，A选项正确。B选项“动物百科全书”范围太广；C选项“太空科学书”重点在太空，而本文重点是恐龙灭绝；D选项“墨西哥旅游杂志”与主题无关。
