Winch vSphere feature satisfies this requirement?

An administrator is configuring a stretched DRS/HA clusters. The administrator wishes to restrict the failover of VMs certain hosts within a given site.

Winch vSphere feature satisfies this requirement?

A.
DRS Storage Groups

B.
DRS Host Groups

C.
Host Priority

D.
Host Affinity

Explanation:
Page 73 from vsphere-esxi-vcenter-server-50-resource-management-guide.pdf DRS Host Group is a prerequisite of VM-Host Affinity rule. In DRS group you will create a list of available hosts from specific virtual machines.