41、【答案】C How do archaeologists know where to find what they are looking for when there is nothing visible on the surface of the ground?

　　【解析】

　　42、【答案】F Most archaeological sites, however, are discovered by archacologists who have set out to look for them.

　　【解析】

　　43、【答案】G Ground surveys allow archaeologists to pinpoint the places where digs will be successful.

　　【解析】

　　44、【答案】D Surveys can cover a single large settlement or entire landscapes.

　　【解析】

　　45、【答案】B In another case, American archaeologists Rene and George Cowgill spent years systematically mapping the entire city of Teotihuacan in the Valley of Mexico near what is now Mexico City.