Which condition is likely preventing the host from entering maintenance mode?

When a vSphere administrator attempts to remediate a host with Update Manager, the host is
unable to enter maintenance mode.
Which condition is likely preventing the host from entering maintenance mode?

A.
A virtual machine on the host has a removable device connected.

B.
A virtual machine on the host is configured to use Fault Tolerance.

C.
A virtual machine is powered off and cannot be migrated to another host.

D.
A virtual machine is configured with a local .vswp file.

Explanation: