Which three statements about bidirectional PIM are true？（）
- ATraffic for a bidirectional group flows along the one shared tree and simultaneously utilizes multiple paths in a redundant network topology
- BIt does not require any traffic signaling in the protocol
- CMembership to a bidirectional group is signaled using explicit Join messages
- DIt maintains source-specific forwarding state
- EIt reduces memory， bandwidth， and CPU requirement