参考答案

正确答案：convinced
convinced 解析：空前的is not和空后的by表明，本空应填一被动形式的动词。这两段表明了Hugh Hendrie对这一研究的态度。题干中的Hugh Hendrie said the study was a nice and good one与第21段首句提到的“It's a nice approach，a very good study,”he said对应，is not为第20段原文信息重现，by its conclusions与by the paper's conclusions对应，故by the paper's conclusions前的convinced即为本题答案。