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: Surgery
A 64 year old hypeensive obsese female was undergoing surgery for fracture femur under general anaesthesia. Intra-operatively her end-tidal carbon dioxide decreased to 20 from 40 mm of Hg, followed by hypotension and oxygen saturation of 85%. What could be the most probable cause? 
Select and explain. 
A. Fat embolism, B. Hypovolemia, C. Bronchospasm, D. Myocardial infarction
A: Fat embolism
Answer: A: Fat embolism 
Explanation: A i.e. Fat embolism