Solution to Exercise:

• All sets are finite sets
• Set D can be classified as a singleton set, because it has only one element
• Sets A and B have the same cardinality of 3 and are thus equivalent sets
• Set A is a proper subset of C, or A ⊂ C
• Set D is a proper subset of both B and C, and so D ⊂ B, D ⊂ C
• Sets A and D are disjoint, because they have no common elements