Correct Answer: ecology

Solution : The correct answer is the second option.

Explanation : In the given group of words, study of the environment, the term that directly pertains to this field of study is ecology . Ecology is the scientific study of the relationships between living organisms and their environments, encompassing both biotic (living) and abiotic (non-living) components. It focuses on understanding how organisms interact with each other and their surroundings.

The meanings of the other options are as follows:

• Pathology : This term refers to the study of diseases.
• Cosmology : This term refers to the study of the universe.
• Radiology : This term refers to the study of medical imaging techniques.

Therefore, the correct one-word substitute is ecology .