Suppose you are standing on the surface z f x y at the point a b f a b Interpret the meaning of f a b and fy a b in terms of slopes or rates of change Choose the correct answer below O A f a b is the slope of the surface in the direction parallel to the y axis and f a b is the slope of the surface in the direction parallel to the x axis both taken at a b OB f a b is the slope of the surface in the direction parallel to the x axis and fy a b is the slope of the surface in the direction parallel to the y axis both taken at x y OC f a b is the slope of the surface in the direction parallel to the x axis and fy a b is the slope of the surface in the direction parallel to the y axis both taken at a b OD f a b is the slope of the surface in the direction parallel to the y axis and fy a b is the slope of the surface in the direction parallel to the x axis both taken at x y