Which of the following statements about dual-system hot standby is correct? (Multiple Choice)

Which of the following statements about dual-system hot standby is correct? (Multiple Choice)
A . The firewall is connected to the router upstream and connected to the Layer 2 switch downstream. OSPF+VRRP can be used to achieve load balancing.
B. When link state detection is enabled, and incoming and outgoing packets are forwarded by the active and standby USGs respectively, and the USG does not enable rate-dependent backup, the TCP service can pass smoothly.
C. The default priority of the Active group is 65001, and the default priority of the Standby group is 65000.
D. The slot numbers of the physical cards of the two devices can be different.

Answer: AC