Mrs. Frank gave her students the function f(x) = 112²+3, and asked her students to write the equation for a function that represents a vertical shift downward for f(x). Katie's function was f(x) = 11x² + 1, Christina's was f(x) = 11x23, and Ali's was f(x) = 112²+5. Who had a correct answer?

A Katie only
B Katie and Christina
(C) Christina and Ali
D Katie, Christina, and Ali