What document serves to summarize a company's financial health and operational viability?

A balance sheet is a key financial document that summarizes a company's financial health and operational viability at a specific point in time. It provides a snapshot of the company’s assets, liabilities, and equity, allowing stakeholders to assess the overall stability and solvency of the business. By examining the balance sheet, one can determine whether the company has enough assets to cover its liabilities, which is critical for understanding its financial position and potential for future growth.

In contrast, a cash flow statement focuses specifically on the flow of cash in and out of a company over a period, detailing how cash is generated and used, but it does not summarize the entire financial health as effectively as a balance sheet. A profit and loss statement, or income statement, summarizes revenues and expenses to show profitability over a period but does not provide a comprehensive view of what the company owns and owes. A market research report, while useful for strategic planning and understanding market conditions, does not address the financial aspects of a company's health directly. Thus, the balance sheet is the most appropriate document for summarizing a company's financial health and operational viability.