A.I. Explanation:

Option 1: "Increasing physical fitness"

Explanation: This option is incorrect because the text does not mention physical fitness as a benefit of night-time sky observation. The focus is on educational and therapeutic benefits, specifically the calming effects and mindfulness associated with stargazing.

Option 2: "Enhancing digital photography skills"

Explanation: This option is incorrect as the text does not discuss digital photography skills. The benefits highlighted are related to knowledge of the cosmos and mental well-being, not photography.

Option 3: "Improving daytime visibility"

Explanation: This option is incorrect because the text does not address daytime visibility. The benefits of night-time sky observation are centered around stress reduction and mindfulness, not visibility during the day.

Option 4: "Reducing stress and promoting mindfulness"

Explanation: This option is correct as the text explicitly states that stargazing provides a calming effect, reducing stress and promoting mindfulness. This aligns with the overall theme of the text, which emphasizes the therapeutic benefits of night-time sky observation.