What designation is applied to information that may cause exceptionally grave damage to national security if disclosed?

The designation that applies to information which, if disclosed, may cause exceptionally grave damage to national security is "Top Secret." This classification is the highest level of sensitive information in the U.S. government and is reserved for data that poses a significant risk to national security if compromised.

Top Secret information encompasses a broad range of sensitive matters, including military plans, intelligence operations, and sensitive diplomatic communications. The rationale behind this classification is that any unauthorized disclosure could severely harm national interests, compromise national defense systems, or jeopardize the safety of individuals working within those sensitive areas.

The other classifications, such as Restricted, Secret, and Confidential, denote lower levels of sensitivity. "Secret" indicates that unauthorized disclosure could cause serious damage, while "Confidential" refers to information that could cause damage, but not necessarily grave damage to national security. The distinction in these levels is crucial for appropriate handling, storage, and dissemination of classified information.