Final answer:
The maximum population size that the deer population reached was 120 individuals, indicating the local environment's carrying capacity.
Step-by-step explanation:
The question asks about the maximum population size that a deer population reached. Based on the provided information, the maximum number of individuals in the deer population became stable after reaching 120. This number indicates the potential carrying capacity of the local environment, which is the maximum population size that the environment can sustain. It is not one of the multiple-choice options provided (A) 100 (B) 500 (C) 1000 (D) 10,000, suggesting there may be an error in the question or the available options. Understanding population dynamics is crucial for managing wildlife and conserving ecosystems.