Which configuration is causing the inability of the virtual machines to communicate?

A virtual machine is unable to communicate with another virtual machine. Both virtual machines are
connected to the Production port group on the same virtual switch and are running on the same
host.
Which configuration is causing the inability of the virtual machines to communicate?

A.
LLDP was enabled instead of CDP for the vSphere Distributed Switch.

B.
Promiscuous Mode has been set to Allow on the Production port group.

C.
The Production port group is configured to use a secondary PVLAN.

D.
The speed and duplex settings for the virtual machine vmnics do not match.