A technician notices that there is a second partition on the primary hard drive. This partitionis notassigned a drive letter and is not accessible from Windows. Which of the following is the MOST likely explanation for this extra partition?（）

A. Space reserved by the drive manufacturer for firmware.
B. Space set aside by Windows for use by the virtual memory swap file.
C. A potentially dangerous virus has been downloaded onto the system.
D. A recovery partition put there by the manufacturer.