The correct option is D All of the above
Derivative of constant is always zero as for a constant function f(x), there is no change in y w.r.t x.
Tangent is the limiting case of secent which intersects the curve at two infinitesimally close points.
Slope is defined as the ratio of the verticle change between two points, to the horizontal change between the same two points i.e. m=ΔyΔx