The research lacks evidence, and therefore, its conclusions are doubtful.
A. solid
B. fierce
C. severe
D. potential
网友回答
A. solid
B. fierce
C. severe
D. potential
解析:根据句意:研究缺乏实证(solid evidence),因此所得出的结论还有待考证。fierce激烈的;severe严重的;potential,有潜力的,均不符合语境,故排除。