Which planet has completed less than one orbit of the sun in the last 100 years?

The Neptune is the planet that has completed less than one orbit of sun in last 100 years.

Explanation:

The orbital period of planets in a solar system are given as follows:

1. Mercury  - 88 days

2. Mars - 687 days

3. Venus - 225 days

4. Jupiter - 12 years

5. Earth - 365 days

6. Saturn - 29 years

7. Uranus - 84 years

8. Neptune - 165 years

9. Pluto - 248 years

Since, pluto is not considered as a planet. So, Neptune is the planet that has completed less than one orbit of sun in last 100 years.

For more details, refer to the link:

link