This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
[{'content': 'Leiden factor is - \nSelect and explain. \nA. Factor VI, B. Factor VIII, C. Factor IV, D. Factor V', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Approximately 2% to 15% of whites carry a specific factor V mutation (called the Leiden mutation, after the Dutch city where it was first described). The mutation alters an amino acid residue in factor V and renders it resistant to protein C. Thus, an impoant antithrombotic counter-regulatory mechanism is lost. Heterozygotes carry a 5-fold increased risk for venous thrombosis, with homozygotes having a 50-fold increased risk. ( Robbins Basic Pathology, 9 th edition, page 87 )', 'role': 'assistant'}]