Final answer:
Zeus placed Callisto in the sky as the constellation Ursa Major or Ursa Minor, represented by a bear, and her son, Arcturus, is her 'keeper' in the stars as part of the Boötes constellation. The correct answer is a) Bear.
Step-by-step explanation:
In Greek mythology, Zeus placed Callisto in the night sky as a bear, making her the constellation we know as either Ursa Major (the Great Bear) or Ursa Minor (the Little Bear), depending on different versions of the myth. Callisto's son Arcturus is represented by a star of the same name, which is part of the constellation Boötes the herdsman, who can be seen as her 'keeper' in the stars. Therefore, the correct answer to the student's question is a) Bear.
The stories of these constellations are part of a rich tapestry of ancient Greek belief systems, where the night sky served as a canvas for their gods, heroes, and mythological creatures. These celestial stories not only gave rise to the names of constellations but also influenced the interpretation of celestial events and the ascribing of certain qualities to the stars.