What best explains why cario, egypt , was a major population center prior to 1500

It is densely populated because the majority of Egypt's population lives around the Nile River and in the north where the climate is somewhat less harsh and there is less desert terrain.

ń, wǒ shuō yīngyǔ, dàn wǒ huì shuō qítā yǔyán, rú xībānyá yǔ fǎyǔ yìdàlì yǔ hé pǔtōnghuà, suǒyǐ bùyào pànduàn, dànshì