Does the equation $y=2\sqrt[\phantom{2}]{x}$ define $y$ as a function of $x?$

A$.$ No$,$ because for any input $x,$ the equation yields more than one output $y.$

B$.$ No$,$ because for any input $x,$ the equation yields only one output $y.$

C$.$ Yes, because any equation in terms of $x$ and $y$ is a function.

D$.$ Yes, because for any input $x,$ the equation yields only one output $y.$