The correct option is D order =2, degree = not defined
[1+(dydx)2+sin(dydx)]3/4=d2ydx2
⇒[1+(dydx)2+sin(dydx)]3=(d2ydx2)4 ⋯(1)
The highest order derivative in the differential equation (1) is d2ydx2, so its order is 2.
Equation (1) is not a polynomial equation in dydx, so its degree is not defined.