Final answer:
The Canadian goose's southward flight in winter best illustrates its response to the environment through migration, which is a part of its metabolic process to maintain life.
Step-by-step explanation:
The behavior of the Canadian goose flying south for the winter to avoid the cold best illustrates the characteristic of response to the environment. This behavior is an example of migration, which is an innate behavior in many animals that is triggered by environmental changes. Migration is an adaptation that helps animals like the Canadian goose cope with issues related to temperature, food availability, and finding mates. While it is not one of the listed choices in the question, it is understood as an aspect of metabolism in a broader sense, as the goose is conserving energy and ensuring survival through behavioral adaptation. Therefore, the closest option provided in the question is option c, metabolism, as this includes all the processes the organism uses to maintain life, including responding to environmental changes.