Concept:Circumnavigation proves that the Earth has no edge and is spherical.
Explanation:Circumnavigation means travelling around the Earth in a continuous path and returning to the starting point.
If the Earth were flat, a traveller would eventually reach an edge and could not continue in the same direction.
But sailors and pilots have successfully gone around the Earth in all directions.
This is only possible because the Earth is a closed, spherical surface.
The variation in day and night length is due to the tilt of the Earth's axis, not its shape.
The rise and fall of tides is caused by the gravitational pull of the Moon and the Sun.
Therefore, circumnavigation is direct proof of the spherical shape of the Earth.
Answer:A. Circumnavigation