Ancient egypt most likely developed along the nile river for which of the following reasons?
the river was used as protection between egypt and their enemies.
the river was considered a focus for religious observances.
the river was important to survival as a source of water for crops.
the river was seen as a boundary between the egyptian social classes.

The third one. The river was used for survival as a source of water for crops.

The Nile river was a source of water to the Ancient Egyptians. They would wait for the river to overflow onto their crops so the river would water them. They would also use reeds they would find near the river to weave them into papyrus paper, (I think that's the name, sorry if I'm incorrect), and they would use the paper to write hieroglyphs on. The river may also have been protection from enimies, but was mainly used for farming.