Both are the components of a sensitivity label.
The following are incorrect:
A Classification Set and a single Compartment. Is incorrect because the nomenclature “Classification Set” is incorrect, there only one classifcation and it is not a “single compartment” but a Compartment Set.
A single classification and a single compartment. Is incorrect because while there only is one classifcation, it is not a “single compartment” but a Compartment Set.
A Classification Set and user credentials. Is incorrect because the nomenclature “Classification Set” is incorrect, there only one classifcation and it is not “user credential” but a Compartment Set. The user would have their own sensitivity label.