Which of the given parameters contribute to an increase in population…

The correct answer is Option (2) → (B) and (C) only

Population density is the number of individuals of a population in a given area. It changes through four basic processes. Two of them add individuals and two remove them.

(A) Mortality — Incorrect. Mortality is the number of deaths in a given period, so it lowers the density.

(B) Natality — Correct. Natality is the number of births, added to the starting density.

(C) Immigration — Correct. It is individuals of the same species coming into the habitat from elsewhere.

(D) Emigration — Incorrect. Emigration is individuals leaving the habitat, so it lowers the density.

NCERT Extract:
Population Growth – “The size of a population for any species is not a static parameter. It keeps changing with time, depending on various factors including food availability, predation pressure and adverse weather. In fact, it is these changes in population density that give us some idea of what is happening to the population – whether it is flourishing or declining. Whatever might be the ultimate reasons, the density of a population in a given habitat during a given period, fluctuates due to changes in four basic processes, two of which (natality and immigration) contribute to an increase in population density and two (mortality and emigration) to a decrease.”