Population ecology considers all of the following

a)what species live in a given area

b)the size of an area in which the species live

c)the overall health of the population of the species

d)how human can completely exterminate a species if necessary

The correct answer is option D which is, "how human can completely exterminate a species if necessary".

Population is the individual relating to the same specie living in the same area at the same time. Like the population of the cats living in the local jungle.

Ecology is the study and observation based study of species and their relation with their natural environment.

Hence population ecology is the study of a single population with respect to their community.

So all above 3 options A, B and C are related to population ecology except option D.