18. To find a state's rate of must be subtracted from its crude birth rate.
a state's crude death rate
19. All populated areas are classified into two categories: urban or

Aeolian processes,  pertain to  wind  activity in the study of  geology  and  weather  and specifically to the wind's ability to shape the surface of the  earth  (or other  planets). winds may  erode, transport, and deposit materials and are effective agents in regions with sparse  vegetation, a lack of soil moisture and a large supply of unconsolidated  sediments. although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as  deserts

Convection current is the main process through which heat is transferred in bulk from one location to another through the cyclic motion of a large volume of substance.