Explanation: During an annual inspection, the goal is to confirm the battery system is ready and capable of powering the station when needed. **D is correct** because it describes a practical test of the battery's ability to deliver power under realistic operating conditions. Taking the battery off charge ensures you're testing its stored energy, not just the charger's output. Applying the maximum required load (e.g., running the radio at full power) and measuring the discharge current verifies that the battery can supply the necessary current for your equipment. This directly assesses the battery's health and readiness to perform its intended function during an emergency or normal operation. **A is incorrect** because measuring specific gravity (for lead-acid batteries) while charging can give inaccurate readings due to gassing and electrolyte agitation. Readings should be taken after a full charge and a rest period. **B is incorrect** as measuring terminal voltage *only* at the end of a long, full-load discharge doesn't provide a comprehensive view of the battery's performance throughout the discharge cycle, nor does it necessarily ensure readiness without fully depleting the battery for the inspection. While useful for capacity testing, it's not the primary "readiness" check for an annual inspection. **C is incorrect** because while specific gravity can be monitored during discharge, it's a specific type of capacity test and, like A, only applies to lead-acid batteries. Answer D provides a more general and immediate operational readiness check applicable to various battery chemistries.