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　　1.A more conclusive answer about life on Mars,past or present, would give researchers invaluable data about the range of conditions under which a planet can generate the complex chemistry that leads to life.

　　2.The Bush administration seems bent on satisfying the small but vocal group of Americans who oppose stem cell research under any conditions.

　　1.【解析】該題考察which引導定語從句的用法。Past or present是插入成分，補充說明life on Mars.which 引導定語從句，修飾conditiona,which在從句中作方式狀語，前面加介詞under.

　　【句意】有關火星上過去和現在是否存在生命的更加確鑿的答案，將向研究人員提供以下方面的珍貴數據，即行星在什么條件下能夠導致最終產生生命的復雜化學反應。

　　2.【解析】該句為主從復合句。主句是the Bush administration seems bent on satisfying the small but vocal group of Americans,定語從句who oppose stem cell research under any conditions來修飾Americans.

　　【句意】少數人呼聲不斷，堅決反對出于任何目的的干細胞研究，布什政府似乎已經屈從于滿足這些人了。