In the Gupta age, Varahamihira wrote the famous book, Brihat Sanhita. This book was a treatise on astronomy. Astronomy is the study of celestial objects, such as stars, planets, and galaxies, as well as the phenomena that occur in space. Varahamihira`s Brihat Sanhita covered various aspects of astronomy, including astrology, eclipses, and planetary movements.

Option 1, astronomy, is the correct answer. This aligns with Varahamihira`s book being a treatise on astronomy, as mentioned in the question.

Option 2, statecraft, refers to the art of governing and managing a state. Although statecraft may have been relevant during the Gupta age, it is not directly related to Varahamihira`s Brihat Sanhita.

Option 3, the Ayurvedic system of medicine, is the traditional Indian system of medicine. While Ayurveda was practiced during the Gupta age, it is not the focus of Brihat Sanhita.

Option 4, economics, deals with the production, distribution, and consumption of goods and services. While economics may have been relevant during the Gupta age, it is not the subject of Varahamihira`s book.

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