We are given the general solution:
\[
y = ae^{2x} + bxe^{2x} + C
\]
Step 1: Differentiate the given solution.
First, find the first derivative of \( y \) with respect to \( x \):
\[
\frac{dy}{dx} = 2ae^{2x} + be^{2x} + 2bxe^{2x}
\]
Step 2: Differentiate again.
Next, find the second derivative of \( y \):
\[
\frac{d^2y}{dx^2} = 4ae^{2x} + 4be^{2x} + 4bxe^{2x}
\]
Step 3: Analyze the order of the differential equation.
Since we need to eliminate the arbitrary constants \( a \), \( b \), and \( C \), the highest derivative we need to take is the second derivative, which is the second order differential equation.
Thus, the order of the differential equation is 2.
Thus, the correct answer is:
\[
\boxed{2}
\]