some people viewed the findings with caution ,noting that a cause-and-effect relationship between passive smoking and cancer remained to be shown .句意:有些人对研究结果谨慎看待,注意到被动吸烟和癌症之间的因果联系还有待发现。这里nothing that a cause-and-effect relationship between passive smoking and cancer remained 结结合前面的意思:之前得出的那些findings,谨慎地来说,就说明一点:被动吸烟和癌症之间的因果联系还有待发现(除了表明这点以外,这些findings意味着nothing)。故本题应选A。
语法知识点:非谓语动词