Final answer:
A "RAID degraded" message upon boot usually indicates a faulty hard drive within the RAID array. This is evidence that one of the drives has failed or is encountering problems, pushing the array to operate in a degraded mode.
Step-by-step explanation:
When a computer boots up with the message "RAID degraded," it typically signifies an issue with one of the drives within the RAID array. This is most likely due to a faulty hard drive. RAID systems are designed to provide increased data reliability and performance by spreading data across multiple drives. When one drive fails or encounters errors, the RAID array can continue operating in a degraded mode, but it is at increased risk of data loss until the faulty drive is replaced and the array is rebuilt.
Answer choices A, B, and C (faulty RAM, faulty RAID battery, and faulty power supply) are not directly related to this specific error message. These components can cause other types of failure or system instability, but they would not typically result in a RAID array being reported as degraded.