How do storage pool thick LUNs affect capacity?

A.
A storage pool thick LUN uses slightly more capacity than the amount of user data written

B.
A storage pool thick LUN uses less capacity than the amount the server operating system sees

C.
Capacity of a storage pool thick LUN uses the same capacity as the server operating system sees

D.
Capacity of a storage pool thick LUN uses less user capacity then a traditional LUN