Final answer:
The arid region and scarcity of water is the geographic factor that affects the people of North Africa the most.
Step-by-step explanation:
The geographic factor that affects the people of North Africa the most is the arid region and scarcity of water.
This region is dominated by the Sahara Desert, which is the largest desert in the world. The lack of water and arid conditions make it difficult for agriculture and human settlement.
As a result, most of the population in North Africa lives along the Mediterranean coast or along the Nile River, where there is access to water and fertile land for farming.