Answer:
Her research most clearly impinges on c. voluntary participation.
Explanation:
Students are free to take part in Professor Smith's study or not. If they decide to do it, their information will remain confidential, which guarantees their anonymity. Professor Smith has explained the study clearly, not having used of deception to get students to participate. We do not know, however, if she will use analysis and reporting. Therefore, the best option is letter c. voluntary participation.