Explanation: Top Secret information is the highest level of classification of material on a national level. Such material would cause “exceptionally grave damage” to national security if publicly available. Answer: A is incorrect. Secret information is that, if disclosed to unauthorized parties, could be expected to cause serious damage to the national security, but it is not the best answer for the above question. Answer: C is incorrect. Such material would cause “damage” or be “prejudicial” to national security if publicly available. Answer: B is incorrect. Unclassified information, technically, is not a classification level, but is used for government documents that do not have a classification listed above. Such documents can sometimes be viewed by those without security clearance.