Answer:
To get crude density, divide the total land area by the total population. You can see that when you measure a large area of land, the arithmetic density becomes meaningless because it “blends in” the urban population and masks the sparsely-inhabited areas with an average.
I think that the two regions would be the Temperate Zone and the Polar Zone, as they're the only climate regions to the south of the 20<span>°S latitude. Check a world latitude map and compare it with a climate map if you're still unsure.</span>
