What is true regarding an IPMP group?

To make IPMP groups persists across reboots you would have to do some work:

To configure an IPMP group that persists across system reboots, you would edit the hostname configuration file of the IPMP interface to add data addresses.

Note: The same (non-null) character string IPMP group name identifies all interfaces in the group. You can place interfaces from NICs of different speeds within the same IPMP group, as long as the NICs are of the same type. For example, you can configure the interfaces of 100-megabit Ethernet NICs and the interfaces of one gigabit Ethernet NICs in the same group. As another example, suppose you have two 100-megabit Ethernet NICs. You can configure one of the interfaces down to 10 megabits and still place the two interfaces into the same IPMP group.

Incorrect:

Not A: You cannot place two interfaces of different media types into an IPMP group. For example, you cannot place an ATM interface in the same group as an Ethernet interface.

Not B: An IP multipathing group, or IPMP group, consists of one or more physical interfaces on the same system that are configured with the same IPMP group name. All interfaces in the IPMP group must be connected to the same IP link.