American researchers studying the effects of physical attractiveness on compliance wish to expand the cross-cultural generalizability of their findings to a Lebanese population. They travel to Lebanon and recruit local residents, whom the American researchers rate as attractive or unattractive, to act as experimental confederates. However, they are unable to replicate their research findings. What is a potential problem with this research?
A. Inter-rater reliability has not been assessed.
B. Language barriers will prevent successful research from occurring.
C. The study may not be reliable due to differences in expectations for compliance between cultures.
D. The study may not be valid due to differences in standards of attractiveness between cultures.