A psychologist is interested in whether the title of an expert impacts people's mask-wearing behaviors. Ten individuals were given a conference on why and how to wear a mask by a professor of medicine, eight individuals were given the same conference by a medical school student, and 11 participants were given the same conference by a school counsellor. After the conference, all participants were given a self-report questionnaire including questions about the effectiveness of the conference and if their behavior could change as a result. Based on the information above, what is the alternative hypothesis? A. At least one mean is different.

B. The professor's conference will be more effective than the others.

C .The professor's conference will be more effective than the medical student's conference.

D .The professor's conference will be more effective than the school counsellor's conference.