Multivalued Dependencies Task

Question

We have R(A,B,C)

1. 1 2 3
2. 1 3 2
3. 1 2 2
4. 3 2 1
5. 3 2 3

Question : Which of the following multivalued dependencies does this instance of R not satisfy?

1. BC ↠ A
2. BC ↠ C
3. C ↠ A
4. ✔ A ↠ B

Right answer is 4 but why i dont understand please explain

Answer 1

It doesn't satisfy statement 4 because for every unique combination of A and B, you have to have matching rows with C.

To make Statement 4 valid, you'd need a 1 3 3 in your table (since you have a 1 2 3).

Good luck.