dated back only to 12,000 years ago和第三段的Their discovery uncovered fishing hooks made from bone that date back to about 42,000 years ago可知，O'Connor的发现把人类开始深海捕鱼的年代提前了3万年。

　　答案：　C

　　3．Why did the ancient people on the island of Timor go fishing according to the text?

　　A．The island was too small for the large population.

　　B．It was very easy to catch fish around the island.

　　C．There were few animals on land for food.

　　D．People there loved eating fish.

　　解析：　推理判断题。根据文章第五段的The island of Timor has very few land animals overall and only small birds call the island home，perhaps explaining why the ancient people here went fishing可推测，这里的陆地动物非常少，所以人们不得不到海中捕鱼充当食物。

　　答案：　C

　　4．The text is probably taken from________.

　　A．an official document B．a scientific article

　　C．a newspaper ad D．a book review

　　解析：　文章出处题。本文是一项科学发现，故选B项。

　　答案：　B

　　Scientists recently discovered that pictures on cave walls at Creswell Crags are the oldest known in Great Britain.But they didn't find out in the usual way.

　　Archaeologists often date cave art with a process called radiocarbon dating.The technique can measure the age of carbon found in charcoal (木炭) drawings or painted pictures.Carbon is an element found in many things，including charcoal and even people.But in this case，there was no paint or charcoal to test.People carved the pictures of animals and figures into the rock using stone tools.The scientists had an "aha！" moment when they noticed small rocks stuck to the top of the drawings.The small rocks must have formed after the drawings were made.

　　"It is rare to be able to scientifically date rock art，" said Alistair Pike，an archaeological scientist at Britain's University of Bristol."We were very fortunate that some of them were covered by stalagmites (石笋)．"

When a test proved that the stalagmites formed 12,800 years ago，the scientists knew the art