Answer : 2. "Honoring the discovery of our planet's activity"
Explanation :

Earth Rotation Day is celebrated every year on 8 January. This special day is dedicated to acknowledging the important discovery of the Earth's rotation on its axis. The theme chosen to celebrate Earth Rotation Day in 2024 is “Honoring the Discovery of the Motion of Our Planet.” This topic invites us to consider the historical journey of understanding the Earth's rotation and the impact this knowledge has had on our understanding.