This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ECG and Arrhythmias 1, Subject name: Medicine
You are asked to review the ECG below, for a 72-year-old male who has presented to ER with falls. Based on your ECG interpretation, what is the likely diagnosis? 
Select and explain. 
A. Hyperkalaemia, B. Second degree - Mobitz Type 2 - hea block, C. First degree hea block, D. Second degree - Mobitz Type 1 - hea block
D: Second degree - Mobitz Type 1 - hea block
Answer: D: Second degree - Mobitz Type 1 - hea block 
Explanation: Missed beat in ECG, PR interval-before & after missed beat are unequal in size-patient have serial prolongation of PR interval F/B drop beat - MOBITZ-I Hea Block