Which Hypothesis Was Supported by the Results of MacDonald's Study

Which hypothesis was supported by the results of MacDonald's study of ADHD in Australia, Norway, Sweden, and the United States?

A) The prevalence of ADHD varies because health care providers in different countries use different definitions and measures of ADHD.
B) ADHD is more noticeable at an early age in countries that teach academic skills to preschoolers.
C) Parents and doctors in some countries underreport the prevalence of ADHD because some societies stigmatize childhood mental disorders.
D) Parents and doctors in some countries overreport the prevalence of ADHD because some societies pathologize the normal behaviors of young children.