Task: Question Answering
Input (English): Question: The initial procedure of choice to investigate a possible obstruction of the biliary tract is: 
 Options:  <1> Hepatobiliary ultrasound. <2> Endoscopic retrograde cholangiopancreatography (ERCP). <3> Colangio Magnetic Resonance. <4> Computed tomography. Abdominal CT <5> Percutaneous transhepatic cholangiography.
Output (English): 1