Why did ancient egypt prosper for such a long period of time in the nile river valley

community, irrigation, and a valuable water source (the Nile river). ... One reason is that the Nile overflowed.

Explanation:  The Nile River literally meant life for ancient Egypt, given that Egypt is in a desert area. By pouring out of the riverbed and flooding the surrounding soil, the Nile applied minerals, which are nutrients that make the soil fertile. This meant rich agricultural yields, an abundance of food and, over time, wealth, which contributed to the development of ancient Egyptian civilization. Under such conditions, Egyptian civilization could only thrive, for it is known that ancient civilizations grew and developed thanks to agriculture, which later enabled every other kind of development. Thus, Egypt also developed an unprecedented civilization marked by many technological, construction, artistic and all other achievements of the time.

the answer is b your welcome : )

profound political, administrative, and social changes in the british isles.