Final answer:
The data likely to be lost if a suspect is using encryption and the device is powered off is the contents of RAM.
Step-by-step explanation:
If a suspect is using encryption, the data in RAM (Random Access Memory) is likely to be lost if the device is powered off. RAM is a type of computer memory that stores data that is being actively used by the computer.
When a device is powered off, the data in RAM is not saved to the hard drive and is therefore lost. Encryption on devices like cell phones, USB thumb drives, and laptop hard drives protects the data stored in these devices, but it does not prevent the loss of data in RAM when the device is powered off.
Therefore, in answer to your question, the contents of RAM (Option C) are likely to be lost if the device is powered off.