When a Swedish ship that sank（沉） in 1628 was recovered from the port of Stockholm, historians and scientists were overjoyed with the chance to examine the remains of the past. The ship construction showed how ships were built and operated during the seventeenth century.  In this way, artifacts, objects made by human beings, provided a picture of daily life almost 400 years ago. Underwater archaeology(考古)-the study of ships, aircraft and human settlements that have sunk under large bodies of water-is really a product of the last 50 years.  The rapid growth of this new area of study has occurred because of the invention of better diving equipment. Besides the Swedish ship wreck(残骸），underwater archaeologists have made more exciting discoveries such as the  5000-year-old boats in the Mediterranean Sea. Underwater archaeology can provide facts abut 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. 小题1: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 小题2:The aim of underwater archaeology is to    . A．exploit(开发)water bodies B．search for underwater life C．study underwater artifacts D．examine underwater environment 小题3: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 D．sold artifacts can hardly be regained for research 小题4:What is the main purpose of the passage? A．To introduce a young branch(分支) of learning. B．To discuss the scientists’ problems. C．To explain people’s way of life in the past. D．To describe the sunken ships.