Task: Question Answering
Input (English): Question: The determination of cyanide by the Liebig method is based on the addition of a silver nitrate standard solution: 
 Options:  <1> Until complete precipitation of silver cyanide. <2> Until the precipitation of silver cyanide begins. <3> Until the appearance of a red precipitate of silver chromate. <4> Until the AgCN complex is quantitatively formed. <5> Until the precipitation of silver iodide, yellow.
Output (English): 2