Question

Which of the following is not a differential equation?

I'm having trouble because they all have derivatives?

A) d^2y/dt^2= t^2+(y/4)

B) 4 +y= 2x+dx/dy

C) t^2= s+(ds/dt)^2

D) (x-x^3)dx= 4-y^2

E) y'=0