The nonlinear equation among the provided options is Option C: y = x^2, as it includes an x squared term, which makes it quadratic in nature and not linear.
The question asks to identify the nonlinear equation among the given options.
A linear equation is generally of the form y = mx + b, where m is the slope and b is the y-intercept, and both m and b are constants.
Looking at the options provided, we know that options A and B are clearly linear because they can be re-written to fit the linear form.
Option C, however, is different because it includes an x squared (x^2) term, which does not fit the linear form and indicates a quadratic relationship.
Therefore, the correct answer to identify the nonlinear equation is: Option C: y = x^2