Arrange the following differential equations in ascending order in accordance to degree
A. $$\left[1 + \left(\frac{dy}{dx}\right)^{2}\right]^{\frac{3}{2}} = \frac{d^{2}y}{dx^{2}}$$
B. $$\left(\frac{dy}{dx}\right)^{5} + y = 0$$
C. $$ \frac{d^{2}y}{dx^{3}} + a^{2}x = 0$$
D. $$ x^{2} \left(\frac{d^{3}y}{dx^{2}}\right)^{3} +y\left(\frac{dy}{dx} \right)^{4}+ y^{4} = 0$$

Choose the correct answer from the options given below: