Final answer:
Chandra Gupta Maurya reacted to the fear of his enemies by strengthening military defenses, implementing strategic alliances, and establishing efficient intelligence networks.
Step-by-step explanation:
The correct answer is d. All of the above. Chandra Gupta Maurya reacted to the fear of his enemies by strengthening military defenses, implementing strategic alliances, and establishing efficient intelligence networks. These measures were aimed at protecting the Mauryan Empire and consolidating its power.