What are two likely reasons for this issue?

An administrator is unable to remove an ESXi 6.x host from a vSphere Distributed Switch.
What are two likely reasons for this issue? (Choose two.)
A. Vmkernel interfaces on the switch are still in use.
B. VM Network port group adapters are connected to different switch.
C. Physical NICs are migrated to different switch.
D. VM Network adapters are connected to this switch.