Final answer:
Among the options given, the astronomical constellation is Mensa.
Step-by-step explanation:
The correct answer is a) Mensa.
Among the options given, Mensa is the only one that is an astronomical constellation. Constellations are groupings of stars that form recognizable patterns in the sky.
In the provided references, it is mentioned that the constellation of Orion, for example, is made up of several recognizable stars, including Betelgeuse and Rigel. It also includes objects denoted by numbers, which are nebulae or gas and dust clouds.