Where does the origin exist on the celestial equator for measuring the longitude?

A)
Ephemeris
B)
Greenwich
C)
Vernal equinox
D)
Intersection of ecliptic and equatorial planes

Correct Answer :   Vernal equinox


Explanation : Vernal equinox lies on the celestial equator which is the outward projection of Earth’s equator on the celestial sphere. This is the origin for measuring the longitude which is done is degrees from east to west.