Which of the following are types of flow control? (Choose three.)（）

A.Layer 2
B.Layer 3
C.Layer 4
D.Layer 5
E.Layer 6
F.Layer 7

A.By default， all defined VLANs are allowed on the trunk.
B.Each single VLAN， or VLAN range， must be specified with the switchport mode command.
C.Each single VLAN， or VLAN range， must be specified with the vtp domain command.
D.Each single VLAN， or VLAN range， must be specified with the vlan database command.

A.It is supplied by the CSU/DSU.
B.It is supplied by the far end router.
C.It is determined by the clock rate command.
D.It is supplied by the Layer 1 bit stream timing.