HSRP gives hosts a resilient default gateway by using a virtual IP address shared by a group of routers. One router is elected active and forwards traffic sent to the virtual gateway; another router waits as standby and takes over if the active router fails. The hosts do not need to know which physical router is active. They continue to use the same default gateway address. That is the central first-hop redundancy model Cisco expects CCNA candidates to understand. HSRP does not synchronize full router configurations, and it does not make every router use the same physical interface address. It also does not inherently load-balance all gateway traffic; classic HSRP is active/standby per group, although designs can use multiple groups for load sharing. The predictable HSRP behaviors are election of active and standby routers, plus use of a shared virtual IP address as the LAN default gateway. Therefore, B and D are the valid choices.