Why Do Most Comets Have Very Elliptical Orbits, Often Extending

Multiple Choice

Why do most comets have very elliptical orbits, often extending far out beyond the orbit of Pluto?

A) They originally formed in circular orbits far from the Sun (> 500 au) , and passing stars have perturbed them into long, elliptical orbits.
B) They are interstellar objects that have been captured in orbit by the Sun.
C) They formed so far from the Sun (e.g., 10,000 au) that their orbits naturally drop deeply into the inner solar system.
D) They originally formed outside the orbit of Pluto and were flung into highly elongated orbits by the giant planets.