What protection method is used in 4F MS-SPRing networks？（）

• A、 Each fiber has half of its capacity reserved for protection.
• B、 Two fibers carry their full capacities while the other two fibers are reserved for protection.
• C、 The signal is sent simultaneously in both directions around the ring. The receiver determines which fiber to listen to based on signal quality.
• D、 The signal is sent simultaneously in both directions around the ring. The transmitter determines which fiber has the working bit set for the receiver to acknowledge.