A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?

Correct Answer: Option B — Measurement of time is along the celestial equator.

The mean sun accounts for Earth's eccentric orbit and axial tilt by moving at a uniform rate along the celestial equator. Measurement along the celestial equator is a consequence, not a cause, of the apparent sun's irregularity.