Final answer:
b) Ship's Store
The Navy Cash merchant that uses a line of accounting to close out each month is the Ship's Store. It utilizes LOA for financial management on naval vessels during monthly closeouts.
Step-by-step explanation:
The student's question asks which Navy Cash merchants use a line of accounting (LOA) to close out each month. Among the options provided, the correct answer is: b) Ship's Store. The Ship's Store operates aboard naval vessels and utilizes LOA for financial management and monthly closeouts. Other options like commissaries, Morale, Welfare, and Recreation (MWR), and Exchange Services have their financial management processes but specifically, within the context of navy cash transactions and the organizational structure on naval ships, the Ship's Store is the one that typically uses LOA for these purposes.