The correct answer is B because the CPU power level exceeds the range normally handled by standard or high-performance air-cooling options for this server design. For HPE ProLiant DL360 Gen11 configurations with very high-wattage processors, HPE design guidance identifies closed-loop liquid cooling as the required or appropriate cooling mechanism for processors at or above the higher thermal threshold. The key phrase in the scenario is that the customer wants to reuse existing third-party, 42U, air-cooled racks with the least amount of change. Closed-loop liquid cooling is self-contained inside the server cooling assembly and does not require the customer to deploy facility-level liquid-cooled racks or direct-liquid-cooling infrastructure. Option A introduces a larger rack and facility change, which violates the ''least amount of changes'' requirement. Option C implies external liquid-cooling infrastructure and is therefore more disruptive. Option D is incorrect because high-performance fans are intended for lower thermal design power ranges and are not sufficient for CPUs exceeding the stated 270-watt threshold. This aligns with the course's ProLiant Gen11/Gen12 server design and validation objectives.