Business \( \square \) are used by businesses to indicate the nature of the underlying business activity and include promissory notes, electron stock certificates, checks, invoices, etc. (Enter one word per blank.)

The correct word to fill in the blank is **instruments**. **Complete Sentence:** Business **instruments** are used by businesses to indicate the nature of the underlying business activity and include promissory notes, electronic stock certificates, checks, invoices, etc. **Explanation:** The term "instruments" refers to various types of legal and financial documents that businesses use to conduct and record transactions. Examples include: - **Promissory Notes:** Written promises to pay a specified amount to a certain individual or entity. - **Stock Certificates:** Documents that represent ownership in a corporation. - **Checks:** Written orders directing a bank to pay money from the writer's account. - **Invoices:** Bills issued by a seller to a buyer indicating items sold and amounts due. All these fall under the category of business instruments because they are essential tools for managing financial and legal aspects of business operations.