Which of the following is a key purpose of classification standards established by Executive Order 13526?

The key purpose of the classification standards established by Executive Order 13526 is to protect national security information. This executive order outlines how information is to be classified, ensuring that sensitive data is properly identified and safeguarded against unauthorized disclosure. The intention is to prevent compromising national security while also balancing the public's need for information. This classification framework informs federal agencies on what information requires protection based on specific criteria, including the potential impact on national security if the information were disclosed.

The other options, while valuable in other contexts, do not align with the primary purpose of Executive Order 13526. For instance, promoting transparency in government operations relates more to open government initiatives than to the classification of sensitive information. Enhancing federal procurement efficiency and standardizing financial reporting practices focus on operational and financial management rather than the protection of national security data. Therefore, the correct emphasis in this context is clearly on securing national security information as specified in the executive order.