The angle measured eastward from the vernal equinox along the celestial equator often expressed in time units is the __________.

Correct Answer: Option C — right ascension

Right ascension is the angular distance measured eastward along the celestial equator from the vernal equinox to the hour circle of a celestial body. It is typically expressed in time units (hours, minutes, seconds) and is a standard coordinate used in celestial navigation to define a body's position.