An administrator attempts to manually reclaim space on thin-provisioned VMFS6 volumes but finds that no
additional space is being recovered.
Which could be causing this?

A.
vSphere 6.5 does not support manual UNMAP.

B.
The manual UNMAP operation has been moved to the vSphere web client.

C.
The VASA version is use is incompatible.

D.
UNMAP is automated for VMFS6.

Explanation:
VMFS 6 is the new filesystem of vSphere 6.5. The new filesystem supports 512e advanced format drives and is
4098 sector (4K) aligned. It also supports automatic UNMAP, which asynchronously tracks freed blocks and
sends UNMAPs to backend storage in background.
https://kb.vmware.com/selfservice/microsites/search.do?
language=en_US&cmd=displayKC&externalId=2147824