Which of the following was a limitation of Asch’s research method?

The limitation of Asch's research method highlighted by the choice concerning the all-male sample is significant because it raises concerns about the generalizability of his findings. Asch conducted his famous conformity experiments primarily with male participants, which can influence the applicability of the results to the broader population. By using only one gender, the study may not accurately represent how different individuals might react in similar situations, especially considering that social influences on behavior can vary across gender. This limitation suggests that the conclusions drawn from Asch's study may not be entirely valid for both men and women, thereby reducing the external validity of the research.

The other choices do involve potential issues, such as the understanding of the task and the setting of the study, but they do not reflect the same level of impact on the overall applicability of the results across diverse groups as the limitation concerning the sample's gender does.