Topic: Substitution, Expression, & Definition,

Best Answer Explained in Below-:

The correct answer to the question 'One who treats cancer patients is called a/an-' is C) Oncologist. An oncologist is a medical professional who specializes in the diagnosis, treatment, and management of cancer. This specialized training allows oncologists to understand the various types of cancers, their potential progression, and the most effective treatment options available, which can include chemotherapy, radiation therapy, immunotherapy, and surgical interventions.

In contrast, the other options refer to different medical specialties:

- A) Pathologist specializes in examining tissues and cells to diagnose diseases, including cancer, but they do not treat patients directly.
- B) Nephrologists are specialists in kidney function and treat conditions related to the kidneys, not cancer.
- D) Neurologists focus on disorders of the nervous system, such as epilepsy or multiple sclerosis, rather than cancer treatment.

By understanding the specific role of an oncologist within the medical community, it becomes clear why they are the designated professionals for treating cancer patients, making option C the correct answer.