Option C is right - Even though HSRP version 2 uses the new IP multicast address 224.0.0.102 to send hello packets instead of the multicast address 224.0.0.2 used by HSRP version 1, when the HSRP version is changed, each group will reinitialize because it now has a new virtual MAC address.

Correct, straight from Cisco; "When the HSRP version is changed, each group will reinitialize because it now has a new virtual MAC address.?" https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipapp_fhrp/configuration/xe-3s/fhp-xe-3s-book/fhp-hsrp-v2.html#:~:text=Version%201%20is%20the%20default,the%20multicast%20address%20of%20224.0.&text=HSRP%20version%202%20permits%20an,MAC%20address%20range%200000.0C9F.

C is correct

The correct answer is C

I confirm the correct option is C, based on the following text: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipapp_fhrp/configuration/xe-3s/fhp-xe-3s-book/fhp-hsrp-v2.html "When the HSRP version is changed, each group will reinitialize because it now has a new virtual MAC address."

Correct option is D.

Agree that C is the correct answer. When it changes, the group reinitializes because it has a new virtual MAC address.

C is right

D is wrong — the multicast address change affects communication, but the main reason for reinitialization is the MAC change.