Final answer:
SCI is marked with specific markings that indicate the classification level and compartments, such as 'TOP SECRET//SCI' followed by codewords for compartment access.
Step-by-step explanation:
Sensitive Compartmented Information (SCI) is marked with specific markings indicating the classification level and compartments. Therefore, the correct answer to how SCI is marked is b) With specific markings indicating the classification level and compartments. This ensures that only individuals with the correct clearance and need-to-know can access the sensitive information. For example, a document might be marked as 'TOP SECRET//SCI' followed by codewords that refer to specific compartments of the SCI. These codewords indicate which portions of the SCI material a person can access. Such careful marking is crucial to maintain information security within governmental and intelligence agencies.