Final answer:
The rationale behind the accounting equation is that a firm must finance the purchase of their assets, and the owners and nonowners should contribute toward it.
Step-by-step explanation:
The rationale behind the accounting equation in the context of the balance sheet is option c: A firm must finance the purchase of their assets, and the owners and nonowners should contribute toward it.
The accounting equation states that assets must always equal liabilities plus owners' equity. This means that the value of a firm's assets is financed by both the owners' investment and any liabilities owed to nonowners.
For example, if a firm purchases equipment for $10,000, they can finance it by investing $5,000 of their own money and borrowing $5,000 from a bank. This way, the assets on the balance sheet (equipment worth $10,000) are financed by the owners' equity ($5,000) and the liability owed to the bank ($5,000).