as far as i understand, the first parameter (first digit in parenthesis) is input data and second one is output data
function must give the same output for the same input. It means, that if you give it 1 and it returns 4, it never can return anything else, no matter how much you try
A.
(6, 5), (1, 1), (6, 4) - twice input 6, and got different answers
B.
(0, 1), (2, 3), (2, 5) - twice input 2, and got different answers
D.
(–2, 3), (–5, 9), (–5, 3) - twice input -5, and got different answers
C.
(8, –2), (–2, 5), (6, 0) - no twice input