The best answer is D. Deploying a dedicated base station and reducing the footprint with highly directional antennas . The biggest risk in the scenario is that unencrypted control traffic is traversing the internet over a cellular network . Since encryption is not feasible, the best compensating control is to reduce exposure by making the wireless path more private, more local, and less accessible to unintended parties. A dedicated base station with directional antennas narrows the RF footprint and reduces interception and unauthorized access opportunities compared with broad internet-based cellular exposure. CompTIA’s SecurityX objectives emphasize Security Architecture , including secure boundaries, compensating controls, and resilient design choices when ideal controls cannot be used.

Why the other options are not best:

A is helpful as a detective control, but it does not reduce the core exposure of unencrypted communications over public infrastructure. B is impractical and technically weak here; standard Cat 5e is not the right medium for a 0.5-mile river crossing. C may detect post-compromise changes, but it does not reduce the likelihood of network compromise in the first place. Because encryption cannot be used, the best risk-reduction strategy is to minimize signal exposure and dependence on public internet-connected cellular paths.