What are the three default roles provided on an ESX Host?

A.
Network Consumer, Datastore Consumer and Resource Pool Administrator

B.
Virtual Machine User, Virtual Machine User and Administrator

C.
Read only, Operator Access and Administrator

D.
No Access, Read Only and Administrator

Explanation:
Mastering VMware vSphere 4, page 387
An ESX/ESXi host has three default roles: No Access, Read-Only, and Administrator