What does the suffix '-ologist' signify?

The suffix '-ologist' signifies a person who specializes in a particular field of study or profession, typically in the sciences or medicine. For example, a biologist studies biology, while a psychologist focuses on psychology. This suffix indicates an individual who has acquired expertise and knowledge in their respective area, often through extensive education and training. The other choices refer to different concepts: medications aid treatment, diagnostic tools help in identifying conditions, and types of diseases represent health conditions without the indication of expertise. Therefore, the correct answer highlights the specialization indicated by the suffix '-ologist'.