Answer: Informed Consent
Explanation: Informed consent in an experiment is defined as gaining the permission from other before conducting any experiment so that participants have the information and know the possible outcomes of the experiment.They are also told about the participation should be voluntary and process of withdrawing from experiment.
According to the case mentioned in the question states about Bob is imparting the knowledge about the experiment's purpose,obtaining the data from participant based on study and the usage of that data. He is also letting them know about backing out process and getting these terms signed on the document in the form of informed consent.