Final answer:
At the occurrence of tactical benchmarks such as shifting from an offensive to a defensive strategy, a Personnel Accountability Report (PAR) should be requested to ensure all team members are accounted for and safe.
Step-by-step explanation:
In the system of accountability, when a tactical benchmark such as a shift from offensive to defensive strategy occurs, it is important to perform a communication check within the system. This ensures that all team members are on the same page and can effectively adapt to the new strategy. While the options given include a rehabilitation assignment, a system communications check, a PAR (Personnel Accountability Report), and a BARKS check, the most appropriate request in this context would be a PAR check (Personnel Accountability Report). This is because a PAR allows for the verification of the safety and location of all personnel, which is critical during any transition in tactics.