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: Dental
A patient complains of sensitivity in a Mandibular premolar. A well condensed class V amalgam restoration was placed in that tooth 5 months ago, with no discomfort for the first 4 months. Since then it has become increasingly sensitive. The problem probably relates to: 
Select and explain. 
A. Marginal leakage, B. Fractured restoration, C. Irreversible pulpal damage, D. Tooth brush abrasion
C: Irreversible pulpal damage
Answer: C: Irreversible pulpal damage 
Explanation: None