Kepler modified copernicus's model of the universe by proposing that the

a. paths of the planets follow an elliptical orbit around the sun.
b. planets follow an elliptical orbit every leap year.
c. planets have their own orbits around themselves as they orbit the sun.
d. planets follow a circular orbit around the sun.

A. paths of the planets follow an elliptical orbit around the sun.

Explanation:

Nicolás Copernicus formulated the heliocentric theory of the solar system, where the Sun is the one in the center with the planets moving around it, contradicting what was believed for the time that it was that the Earth was in the center and both the Sun and the planets revolved around him (geocentrism).

This was the basis for Kepler finally describing the planetary movement based on 3 mathematical expressions. These expressions start by saying that the orbits were not circular, if not elliptical, so that the planets are governed by the Pythagorean laws of harmony. His studies showed that the distances of the planets to the Sun drew parallel spheres, being the first to draw the concentric orbits of the planets in their orbits around the Sun.

Kepler's laws are the following:

  - First law. The planets move in elliptical orbits, the sun being one of the foci.

  - Second law. The radius vector that joins the center of the Sun with the center of a planet describes equal areas in equal times.

  - Third law. The squares of the periods of the planets are proportional to the cubes of their distance from the Sun.

it is the second option.