This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hematology, Subject name: Pharmacology
[{'content': 'Which of the following statements about warfarin group of oral anticoagulants is FALSE? \nSelect and explain. \nA. They interfere with an early step in the synthesis of clotting factors, B. Irrespective of the dose administered, their anticoagulant effect has a latency of onset of 1-3 days, C. Their dose is adjusted by repeated measurement of prothrombin time, D. They are contraindicated during pregnancy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Activation of factor II, VII, IX and X are inhibited by warfarin group of oral anticoagulants in presence of vitamin K These anticoagulants do not affect the synthesis of these factors.', 'role': 'assistant'}]