In which of the following sets A B is equal to B A?

• A. A = {1, 2, 3}, B = {2, 3, 4}
• B. A = {1, 2, 3}, B = {1, 2, 3, 4}
• C. A = {1, 2, 3}, B = {2, 3, 1}
• D. A = {1, 2, 3, 4, 5, 6}, B = {2, 3, 4, 5, 1}