The density of a population in a given habitat during a given period, fluctuates due to changes in four basic process. On this basis fill up A and
(a) A = Natality + Immigration, B = Mortality + Emigration
(b) A = Natality + Mortality, B = Immigration + Emigration
(c) A = Birth rate + Death rate, B = Migration + Emigration
(d) A = Natality + Emigration, B = Mortality + Immigration
