Which is the definition of hyperbola?
A)it is a locus of points that is equidistant from a fixed point called center.
B)It is a locus of points such that the sum of its distance from two fixed points (foci) is constant.
C)It is a locus of points such that its distance from focus plus its distance from a directrix is constant.
D)It is a locus of points such that the difference of each point's distances from two fixed points is constant.
