For What X Is the Function Defined $$y = \sqrt { - 9 x }$$

Multiple Choice

For what x is the function defined? $$y = \sqrt { - 9 x }$$

A) $0 \leq x$
B) $x \geq 3$
C) $x \neq 9$
D) $0 \geq x$
E) The function is undefined for any x.