This physical characteristic most affects the settlement patterns of north africa and southwest asia. loess oil siroccos water

The best answer to the question: This physical characteristic most affects the settlement patterns of North Africa and Southwest Asia, would be: Water.

Explanation:

Along with food supplies, and food sources, most human settlements were also affected by the availability of water sources in any given region on the planet. If such water sources were scarce, or not present, the likelihood of human settlements establishing there permanently, was less likely.

In North Africa and Southwest Asia, this situation of dryness, of lack of water availability, and the locations where water WAS actually present, defined how humans settled in these regions. And because North Africa and Southwest Asia are among the driest regions in the world, human settlement in these two places focused on finding the areas where water was available and settled permanently there. This is why the correct answer is water.