Refer to the Exhibit.
Based on the exhibit, which statement about the Layer 2 topology is true?
A.
A port on switch 3 or switch 4 towards the CST root (switch 6) is blocking traffic.
B.
A total of 64 MST instances for MST region A and region B can be configured.
C.
MSTI BPDUs are exchanged between MST regions and the CST root bridge.
D.
IST BPDUs are exchanged between switch 1 and switch 2 + switch 6 and 7 only.