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: Radiology
Most sensitive investigation for air embolism is 
Select and explain. 
A. Decreased tidal volume of CO2, B. Decreased tidal volume of NO2, C. Doppler ultrasound, D. Central Venous Presure
C: Doppler ultrasound
Answer: C: Doppler ultrasound 
Explanation: C i.e. Doppler Ultrasound