Which Equation Does Not Represent Y as a Function of X

Multiple Choice

Which equation does not represent y as a function of x?

A) $x = 2 y + 5$
B) $x = 6$
C) $y = - 5 x - 7$
D) $y = \left| 6 + 9 x ^ { 2 } \right|$
E) $y = \sqrt { - 8 + 4 x }$