Which marking would be used for information indicating a risk to national security if disclosed?

The marking that would be used for information indicating a risk to national security if disclosed is "TOP SECRET." This classification is reserved for information that, if made public, could cause exceptionally grave damage to national security. The "TOP SECRET" marking is employed for the most sensitive information, which means it warrants the highest level of protection to prevent unauthorized access or disclosure.

In the context of national security, it is crucial to distinguish between various levels of classification. While "CONFIDENTIAL" is used for information that could cause damage to national security if disclosed, "TOP SECRET" indicates a higher degree of sensitivity and potential risk. It is understood that this category requires strict handling protocols due to the severity of the consequences related to its unauthorized disclosure.

The other options do not fit the criteria for handling information that poses a significant risk to national security. "PUBLIC" and "UNCLASSIFIED" indicate that the information is available for general distribution without any security concerns, while "CONFIDENTIAL" signifies damage but does not align with the highest level of risk associated with "TOP SECRET." This is why "TOP SECRET" is the appropriate marking for the information described.