This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Which of the following variables is measured on the ordinal scale \nSelect and explain. \nA. Type of anemia, B. Severity of anemia, C. Hemoglobin level, D. Serum ferritin level', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]