Give four ways to demonstrate that earth is spherical.

Explanation:

1. Watch a ship go off sail. If you ever watch a ship ,go of for sail into the vast ocean, watch its mast and flag, after going to a considerable distance, the mast and flag appear to sink in the ocean to a distant observer. This phenomenon can only  be explained in spherical planet.

2.Lunar Eclipse. Lunar Eclipse occur when Earth is between Sun and the moon. The Earth casts a shadow on the moon. The Shadow is always round and only a spherical object can cast a round shadow.

3. Watch the Sunset: Suppose you on the 10th of the building, in the balcony,to watch the sunset. Lie down on your stomach and watch the sink into the horizon, now stand up ,on standing we can still see the sun over the horizon. This happens because Earth is spherical, on standing up your line of sight changes hence, sun appears to be unset. Had the sun been flat it would have not been possible.

4.Climb a Tree: Imagine a vast plane with  one tree standing in the middle. now if the Earth were flat, our vision would extend exactly as far, while standing at the base of the tree as it would when at the top of the tree. However, the farther we climb, the farther our line of sight will extend to the horizon.

That is because part of Earth that was concealed from view by its curvature is now revealed because our position has changed.

i think the answer is b