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: Medicine
[{'content': 'Fixed PR interval with occasional dropped beats in 2:1, 3:1 or 4:1 pattern with wide QRS complex is seen in: \nSelect and explain. \nA. Wenckebach, B. Mobitz type II, C. WPW syndrome with reentrant tachycardia, D. Complete hea block with atrial fibrillation', 'role': 'user'}, {'content': "Answer: B \nExplanation: Type 1 Second-degree AV block, (Mobitz Type I) Wenckebach periodicity characterized by progressive prolongation of the PR interval followed by a blocked P wave (i.e., a 'dropped' QRS complex). After the dropped QRS complex, the PR interval resets and the cycle repeats. Mobitz II hea block is characterized intermittently nonconducted P waves not preceded by PR prolongation and not followed by PR shoening. Ref: Harrison, Edition 18, Page -1871", 'role': 'assistant'}]