Which of the following explains the discrepancy?

A storage administrator in a virtualized environment has been told by a user that there is no space left on the volume to which the user can write. However, a check reveals that there is 20GB of unused space.

Which of the following explains the discrepancy?
A . The drive is not formatted
B . The drive is thin provisioned
C . The drive is thick provision eager zeroed
D . The drive space is overallocated

Answer: B