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While reproductive strategies are significant in life histories, they ignore important issues like limited resources and competition. The management of population growth by these parameters can be used to establish the concept of K-selected vs r-selected species, which is a classic concept in population biology.

The idea refers to a species' reproductive tactics, environment, and behavior, particularly in terms of resource acquisition and child care. It also takes into account aspects like life expectancy and survival. Although the categories are truly two extremes of a continuum, population biologists have divided species into two main categories: K-selected and r-selected.

Option a - A density-dependent factor is any force that affects the size of a population of living things in response to population density. Excessive population density, for example, causes lemmings to disperse in huge groups in search of a new, less crowded home.

Option b - A density-independent factor, is any force that affects the size of a population of living things regardless of its density. For example, if oxygen concentrations fall or breathable oxygen becomes suddenly unavailable, such as when oxygen-using plants are flooded, organisms for which oxygen is a density-independent factor will perish, and populations of the many affected plant species would decline.

Option c -r-selected species are those that seek out sparsely populated ecological niches in order to exploit them and produce a large number of small-sized progeny with reduced survival rates due to short gestation periods and early maturity. Examples of r-selected species include pest organisms, such as rodents, insects, and weeds.

• The population size of k-selected species grows exponentially until the niche's carrying capacity is reached. To facilitate appropriate embryological development, these species produce a few large-sized progenies and have extended gestation periods.
• Elephants, humans, and bison are all k-selected species. Humans are grouped under primates. Hence, Option (d) is the correct answer.