1- which conic section is defined as the set of all points, the sum of whose distances from two fixed points, called foci, is constant?

a) circle b) parabola c) hyperbola d) elipse

2- Which conic section is defined as the set of all points the difference of whose distance from two fixed points, called the foci, is a constant?

a) circle b) parabola c) hyperbola d) elipse