Correct answer is (a) f(x,y)=ay^n+(bx+c) y^n-1+(dx^2+ex+f) y^n-2+⋯+un (x)=0
Easiest explanation: Plane algebraic curve of nth degree is represented by,
f(x,y)=ay^n+(bx+c) y^n-1+(dx^2+ex+f) y^n-2+⋯+un (x)=0
Where a, b, c, d, e, f are all constants and un(x) is a polynomial in x of degree n.