Concept:Degree of a differential equation is the power of the highest order derivative after the equation is free from radicals and fractions.Explanation:Given equation: (dx2d2y)23=(dxdy)25To remove the fractional powers, square both sides:(dx2d2y)3=(dxdy)5The highest order derivative is dx2d2y and its power is 3.Thus, the degree is 3.Answer:A. 3