This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hemoglobinopathies: Sickle cell anemia, Subject name: Pathology
A 23-year-old female presented with jaundice and pallor for 2 months. Her peripheral blood smear shows the presence of spherocytes. The most relevant investigation to arrive at a diagnosis is which of the following? 
Select and explain. 
A. Tests for PNH, B. Osmotic fragility test, C. Coombs test, D. Reticulocyte count
C: Coombs test
Answer: C: Coombs test 
Explanation: Coombs test going to be positive in autoimmune hemolytic anemia; negative in hereditary spherocytosis. Thus, a differentiation between these conditions can be done.