Task: Text Categorization
Input (English): Question: The initial procedure of choice to investigate a possible obstruction of the biliary tract is: 
 Options:  <0> Hepatobiliary ultrasound. <1> Endoscopic retrograde cholangiopancreatography (ERCP). <2> Colangio Magnetic Resonance. <3> Computed tomography. Abdominal CT <4> Percutaneous transhepatic cholangiography.
Output (English): medicine