Refer to the exhibit. In the diagram， the switches are running IEEE 802.1s MST. Which ports are in the MST blocking state？（）
- A GE-1/2 and GE 2/1
- B GE-1/1 and GE-2/2
- C GE-3/2 and GE 4/1
- D no ports are in the blocking state
- E There is not enough information to determine which ports are in the blocking state.