Final answer:
Option E is not a differential equation because it does not involve any derivatives.
Step-by-step explanation:
A differential equation is an equation that relates a function and its derivatives. To determine if an equation is a differential equation, we need to check if it involves derivatives.
Option A, B, C, and D all involve derivatives, so they are differential equations. However, option E does not involve any derivatives. It is just a simple equation that states y' (the derivative of y) is equal to 0. Therefore, option E is not a differential equation.