What potential sources of bias were present, if any? Select all that apply. A. Individuals may have not been available when the researchers were calling. Those individuals that were available may have not been representative of the population. B. Individuals may have refused to participate in the sample. This may have made the sample less representative of the population. C. No one talks honestly about their exercising habits with people they do not know because it is too personal a subject. This may have led to untrue responses to the survey question. D. Telephone sampling only includes people who had telephones. People who owned telephones may have been older or wealthier on average, and may not have been representative of the entire population. E. There were no potential sources of bias