Which of the following is consistent with this instance of R(X, Y, Z): (1, 1, a), (1, 1, a), (2, 1, b), (3, 2, b)?

1. AX → Y, Z → X
2. BY → Z, Z → X
3. CX → Y, X → Z
4. DY → X, X → Z

Pick an option to check yourself, or open the answer below.

Show answer & explanation

Correct answer: C. X → Y, X → Z

Explanation

Equal X values always have equal Y and Z, so X → Y and X → Z hold. Z = b appears with X = 2 and 3 (Z → X fails), and Y = 1 appears with X = 1 and 2 and Z = a and b (Y → X and Y → Z fail).