What would cause a vSAN: Basic (unicast) connectivity check failure in vSAN Health Check?

What would cause a vSAN: Basic (unicast) connectivity check failure in vSAN Health Check?
A. One or more hosts in the cluster are unable to ping the vSAN VMkernel adapters of other hosts in the cluster.
B. The throughput of the physical network supporting vSAN traffic is less than the recommended minimum throughput.
C. The vSAN VMkernel adapter is shared with another service such as vMotion.
D. vSAN is configured to use multicast to transmit data.