Which of the following differential equations has the solution y=3x2?

• A. ( frac{d^2 y}{dx^2} )-6x=0
• B. ( frac{dy}{dx} )-3x=0
• C. x ( frac{d^2 y}{dx^2} ) ( frac{dy}{dx} )=0
• D. ( frac{d^2 y}{dx^2}- frac{3dy}{dx} )=0