What information determines which datastore will be used for vSphere HA heartbeats?

A.
The number of datastores connected to an ESXI host

B.
The number of ESXi hosts connected to a datastore

C.
The storage protocol used

D.
The type of datastore

Explanation:
http://pubs.vmware.com/vsphere-50/index.jsp?topic=/com.vmware.vsphere.vcenterhost.doc_50/GUID- 3B5AF2B1-C534-4426-B97A-D14019A8010F.html

http://www.yellow-bricks.com/vmware-high-availability-deepdiv/#HA-50heartbeats