The tropical year differs from which year by 20 minutes?

Correct Answer: Option D — Sidereal year

The tropical year, measured between successive vernal equinoxes, is approximately 365 days, 5 hours, 49 minutes. The sidereal year, measured against fixed stars, is 365 days, 6 hours, 9 minutes. The resulting difference is exactly 20 minutes due to the precession of the equinoxes as explained in Bowditch.