Final answer:
The correct answer is A. End of the study.
Step-by-step explanation:
The correct answer is A. End of the study.
According to the regulations set by the Food and Drug Administration (FDA), all unused investigational agents are expected to be returned to the sponsor at the end of the study. This is to ensure proper disposal or redistribution of the agents. Returning unused investigational agents to the sponsor helps maintain accountability and prevents potential misuse or unauthorized distribution of the agents.
For example, if a clinical trial is evaluating a drug's effectiveness in treating a specific medical condition, the unused investigational agents that were provided to the trial participants would need to be returned to the sponsor once the study is complete or terminated.