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
The periapical radiograph of RCT treated tooth shows wiggly apical seal of master cone is due to: 
Select and explain. 
A. Apical perforation of master cone, B. Excess cement in apical region, C. Obstruction of master cone at apical third, D. Short master cone in apical third
D: Short master cone in apical third
Answer: D: Short master cone in apical third 
Explanation: None