There is not enough information in the question to provide a 100% correct answer. You can assign licences to any group created within the Azure AD portal. These can include security groups, Microsoft 365 groups, and either assigned or dynamic groups. You can even create a dynamic device security group and assign E5 licences to it, which doesn't make sense but is true (I've tested it).

However, the missing bit of information is whether the Microsoft 365 groups have the "SecurityEnabled" attribute set to True. Only M365 groups that have the "SecurityEnabled" attribute set to True can have licences assigned to them. If the group is created in the M365 Admin Centre, then the "SecurityEnabled" attribute is set to False and you can not assign licences to the group. But if the M365 group is created in the Azure AD portal, then the "SecurityEnabled" attribute is set to True and you can assign licences.

For the answer, I would make an assumption that because this is an Identity-related exam testing us on Azure AD topics, that the M365 groups were created in the Azure AD portal and therefore have the "SecurityEnabled" attribute set to True. Which means the correct answer is B - all groups...