Final answer:
Overpopulation often leads to increased competition for limited resources, such as food, water, and space. When resources are insufficient, it can lead to starvation of animals, disease spreading quickly, and a leveling off of the population due to decreased chances of mating and increased chance of offspring dying.
Step-by-step explanation:
The correct answer is A. decreased competition.
Overpopulation often leads to increased competition for limited resources, such as food, water, and space. As a result, competition among individuals actually increases rather than decreases. When resources are insufficient to meet the needs of the population, it can lead to starvation of animals, disease spreading quickly, and a leveling off of the population due to decreased chances of mating and increased chance of offspring dying.