The correct answer is A) Because the tank receives high pressure drains. The deaerating feed tank is a critical component in a marine steam plant, and it requires a relief valve to protect it from excessive internal pressure. This is necessary because the tank receives high-pressure drains from various sources, such as steam traps and condensate returns. These high-pressure drains can potentially build up pressure within the tank, which could lead to structural damage or even a catastrophic failure if not properly relieved. The other answer choices are incorrect because they do not address the primary reason for the relief valve. The tank draining to the main condenser (B), receiving large amounts of water (C), or receiving auxiliary exhaust (D) do not directly contribute to the need for a relief valve in the same way that high-pressure drains do.