Which option could be used for vSphere HA heartbeats?

A.
An iSCSI LUN used for booting the master ESXi host.

B.
An iSCSI LUN backing an RDM connected over 10GB Ethernet

C.
An NFS datastore shared with the all hosts, sync, no_root_squash and read only options

D.
A Fibre Channel LUN on an 8GB active/active array backing a VMFS5 datastore