if y is a function of x, which of the following cannot be true?

A. When x = 3 and x = 7, then y = 2.

B. When x = 3, then y = 7 and y = 2

C. When x = 3, then y = 0, and when x = 0, then y is undefined.

D. When x = 3, and x = 7, then y is undefined.