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？（）

• A、Interfaces 11 and 12
• B、Interfaces 1， 2， 3， and 4
• C、Interfaces 5 and 6
• D、Interfaces 5， 6， 7， and 8
• E、Interfaces 1 and 2
• F、Interfaces 1， 3， 5， and 6