One dimensional wave equation is

A

$$\frac{\partial^2 y}{\partial t^2} = \propto^2 \frac{\partial^2 y}{\partial x^2}$$

B

$$\frac{\partial y}{\partial t} = \propto^2 \frac{\partial^2 y}{\partial x^2}$$

C

$$\frac{\partial^2 y}{\partial t^2} + \frac{\partial^2 y}{\partial x^2} = 0$$

D

none of these