The correct answer is A) an atmospheric drain tank trap frozen in the closed position. Explanation: A frozen atmospheric drain tank trap in the closed position would prevent water from properly draining from the main feed system, causing excessive water loss. The other options are not directly related to excessive water loss from the main feed system. A leak in the desuperheater gasket or a vapor bound main condensate pump would not necessarily lead to excessive water loss. Excessive recirculation of condensate from the air ejector condenser back to the main condenser may increase water levels, but would not directly cause excessive water loss from the main feed system.