An Explanation for Why Cross-Cultural Research on Moral Development Has

An explanation for why cross-cultural research on moral development has not found that everyone reaches the highest stage of moral reasoning is that

A) people in many cultures are reluctant to answer questions about hypothetical dilemmas.
B) the interviewers did not do a good job of making the participants comfortable before the interviews began.
C) the measure of moral reasoning used in this research may be biased because it reflects Western and urban cultural values.
D) the research frequently used interviewers who were from different ethnic backgrounds than the people they interviewed.