Answer:
b) A series of stars that form a figure
Explanation:
In astronomy, <em>a constellation is any of certain groupings of stars that form an imaginary outline or pattern on the celestial sphere. </em>They are useful to track artificial satellites and in assisting astronomers and navigators to locate certain stars, therefore constellation is a series of stars that form a figure. A constellation can't be a region of the celestial sphere and all of the stars in it because not all stars in the celestial sphere form figures.
They are no figures in the night sky because constellations are starts, therefore they are present during day or night, it's not a term applicable to astrology because this is a pseudoscience not based on facts, like astronomy.
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