wreck(残骸)，underwater archaeologists have made more exciting discoveries such as the 5,000­year­old boats in the Mediterranean Sea.

Underwater archaeology can provide facts about the past.In ancient ports all over the world are ships sunken in the past 6,000 years.There are also sunken settlements in seas and lakes telling of people's way of life and their systems of trade in ancient times.Underwater archaeologists want to study these objects to add to the world's knowledge of history，but they have to fight two enemies.One enemy is treasure hunters who dive for ancient artifacts that they can sell to collectors.Once sold，these objects are lost to experts.The second enemy is dredging machines(挖掘机) often used to repair ports.These machines destroy wrecks and artifacts or bury them deeper under sand and mud.By teaching the public about the importance of underwater "museums" of the past，archaeologists are hoping to get support for laws to protect underwater treasures.

5．What purpose does Paragraph 1 serve in the passage?

A．To provide background information of the topic.

B．To attract readers' attention to the topic.

C．To use an example to support the topic.

D．To offer basic knowledge of the topic.

答案　B

解析　推理判断题。本文以在海底发现一艘沉船开篇，其目的就是引起读者的兴趣。

6．The aim of underwater archaeology is to .

A．exploit water bodies

B．search for underwater life

C．study underwater artifacts

D．examine underwater environment

答案　C

解析　细节理解题。从最后一段可知，水下考古的目的是研究在很久以前被淹没在水下的一些物品，进而研究当时的历史情况。

7．Underwater archaeologists are worried because .

A．sea hunters have better diving equipment

B．their knowledge of world history is limited

C．dredging machines cause damage to the ports