【单选题】
Refer to the exhibit. In the diagram, the switches are running IEEE 802.1s MST. Which ports are in the MST blocking state?（）<img height="428" src="https://nimg.ppkao.com/2018-07/lina/2018072317220752705.jpg?sign=31dde747525d7a779469799a5a13b0cd&t=62d1cbef" width="665" />
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
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