According to kepler, what do all bodies in orbit around another have in common?

a.
all follow a circular path around a central body, which is the focal point of the circle.

b.
all follow a path tangent to a circle around a central body or focal point.

c.
all follow a spherical path that has a focus on each of two equidistant axes.

d.
all follow an elliptical path that has two foci, rather than a circular path.