Study the exhibit shown below carefully. In this scenario the service provider wants to ensure that switch S1 is the root switch for its own network and the network of . On which interfaces should root guard be configured to ensure that this happens？（）
- AInterfaces 11 and 12
- BInterfaces 1， 2， 3， and 4
- CInterfaces 5 and 6
- DInterfaces 5， 6， 7， and 8
- EInterfaces 1 and 2
- FInterfaces 1， 3， 5， and 6