What are the HRP backup methods supported by the USG?

Note: The HRP backup channel configuration of the active and standby USGs must be the same. The HRP backup channel interfaces of the active and standby USGs must be directly connected. The switch cannot be connected in the middle. The HRP backup channel interface cannot be a Layer 2 switch interface or a Vlanif interface. The USG supports the use of an Eth-Trunk interface as an HRP backup channel, which improves reliability and increases the bandwidth of the backup channel. There are three ways to back up HRP in the textbook: real-time backup, fast backup, and batch backup. After consulting the data, there are four persuasive arguments: one is fast backup; the other is batch backup; the third is manual backup; the fourth is automatic backup--the default backup mode when HRP function is enabled. Therefore, the answer is ABC