Group3: Group1, Group2, Group4, and Group5 only. Group5: Group4 only.

Group nesting in AD DS is governed strictly by group scope, independent of whether a group is security- or distribution-type. A Domain Local group can contain user accounts, Global groups from any domain, and Universal groups from any domain, plus other Domain Local groups from its own domain only. Group3 is a Domain Local group in contoso.com, so it can accept Group1 (Universal, contoso.com), Group2 (Global, contoso.com), and Group4 and Group5 (both Global, canada.contoso.com), since Global groups from any domain are valid Domain Local members. It cannot accept Group6, because Group6 is Domain Local in canada.contoso.com, a different domain, and Domain Local groups may only nest other Domain Local groups from their own domain. That gives Group3: Group1, Group2, Group4, and Group5 only. A Global group, by contrast, can contain only user accounts and other Global groups from the same domain. Group5 is Global in canada.contoso.com, so among the remaining groups only Group4 qualifies, since it is also Global and in the same domain; Group1 (Universal), Group2 (Global but a different domain), and Group6 (Domain Local) are all excluded by scope rules. That gives Group5: Group4 only.