The correct answer to the question is option 3, Autecology. Autecology refers to the study of a single species and the environmental factors that influence its behavior, distribution, abundance, and adaptations. This branch of ecology focuses on understanding the ecological relationship between an individual species and its habitat.

Option 1, Genecology, is incorrect. Genecology is the study of the genetic variation within population of a species in relation to their environment.

Option 2, Synecology, is also incorrect. Synecology, also known as community ecology or population ecology, is the study of the interactions among different species in a community or ecosystem.

Option 4, Ethology, is unrelated to the question. Ethology is the scientific study of animal behavior, particularly in natural environments.

In summary, the study of a single species and its habitat is called Autecology.