The least eccentric orbit corresponds to the lowest value of eccentricity (e).
Among the given options:
- e = 0.001 (very close to a circular orbit)
- e = 0.25 (less eccentric than a more highly elliptical orbit)
- e = 0.90 (more eccentric)
- e = 1 (parabolic trajectory, not an orbit)
The least eccentric orbit is e = 0.001.