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: Biochemistry
Sickling in 'Hbs' disease is primaily caused by 
Select and explain. 
A. Decreased Solubility, B. Decreased Stability, C. Altered function, D. Altered O2 binding capacity
A: Decreased Solubility
Answer: A: Decreased Solubility 
Explanation: The primary pathophysiological event in sickling is intracellular polymerization of deoxy-HbS due to its markedly reduced solubility.