What constitutes commercial paper?

Commercial paper refers specifically to a type of negotiable instrument that allows for the transfer of money through written promises or orders. The correct choice highlights the key characteristics of commercial paper, which include being an unconditional written promise to pay a sum of money. This means that the obligation to pay does not depend on any external conditions; it is straightforward and clear-cut.

In the realm of finance and law, commercial paper is essential for facilitating transactions and providing liquidity in the marketplace. It typically includes instruments like promissory notes and checks, which individuals or businesses use to conduct their financial affairs.

The other options, while they may pertain to various legal or financial concepts, do not specifically define commercial paper. An enforceable agreement by law refers to contracts in general, a conditional promise does not align with the unconditional nature required for commercial paper, and a legal procedure for filing complaints pertains to litigation rather than financial instruments. Thus, the focus on the unconditional aspect of the promise in the correct answer is what makes it the appropriate definition of commercial paper.