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: Medicine
A 20 year old female presenting with anemia, mild jaundice for 2 years, peripheral smear showing sperocytes, the best investigation to be done is - 
Select and explain. 
A. Reticulocyte count, B. Osmotic fragility test, C. Coombs test, D. Bone marrow aspiration
C: Coombs test
Answer: C: Coombs test 
Explanation: None