Improving employee training and awareness is the best option to address the issue of sensitive reports being disclosed via file sharing services. By educating employees about the risks of unapproved file sharing, the security protocols to follow, and the proper channels to use for sharing company information, an organization can significantly reduce the risk of sensitive data being accidentally or intentionally shared on insecure platforms. This human-centric approach addresses the root cause of the problem. Options A, C, and D are security controls that do not directly address the behavior of sharing sensitive files on unauthorized services.