The Reason Leap Years Have an Extra Day Is to Account

Multiple Choice

The reason leap years have an extra day is to account for the fact that the

A) Earth's rotation period is slowly increasing because of tidal effects.
B) year is not exactly equal to an integral number of days.
C) day is not exactly 24 hours because of Earth's periodically varying rotation period.
D) length of the year varies with a period of four years because of precession.