Which priority is correct for the passive firewall?

An administrator has been asked to configure active/passive HA for a pair of Palo Alto Networks NGFWs. The administrator assigns priority 100 to the active firewall.

Which priority is correct for the passive firewall?
A . 0
B . 99
C . 1
D . 255

Answer: D

Explanation:

Reference: https://www.paloaltonetworks.com/content/dam/pan/en_US/assets/pdf/framemaker/71/pan-os/pan-os/section_5.pdf (page 9)