单项选择题
The results of this study might be challenged on the basis that the population tested was small and not random (all participants enrolled in the same course).
A、I
B、M
C、R
D、D 无解析
The results of this study might be challenged on the basis that the population tested was small and not random (all participants enrolled in the same course).
A、I
B、M
C、R
D、D 无解析
