This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthesia Q Bank, Subject name: Anaesthesia
An 85 yr old lady with history of fracture neck of femur, during GA under halothane anesthesia for internal fixation of fracture suddenly develops severe hypotension, bradycardia, capnogram shows sudden fall end tidal carbon dioxide, and most probable diagnosis is:- 
Select and explain. 
A. Myocardial infarction, B. Pulmonary thromboembolism, C. Hypothermia, D. Massive blood loss
B: Pulmonary thromboembolism
Answer: B: Pulmonary thromboembolism 
Explanation: None