Dr. Fishkill is conducting a research study investigating racism among high-school students. His research method involves sitting down with volunteer students whose parents have given consent,

and asking them questions about their beliefs regarding race. Whenever he asks a question that might reveal some level of racism, he unconsciously cocks one eyebrow and lowers his voice slightly. As a result, his research showed that virtually none of his participants held any racist beliefs. What error has Dr. Fishkill made in his method?
a. He has allowed observer-expectancy effects to cloud his results.
b. He has failed to carefully observe his participants.
c. He has failed to control the environment in which the study was taking place.
d. He has failed to use random assignment of his participants.

A