Task: Question Answering
Input (English): Question: Which of the following reactions of drug metabolism has an oxidation reaction as an intermediate step ?: 
 Options:  <1> The transformation of a nitro group (for example, the one existing in nitrofurantoin) into amino. <2> The O-demethylation of an ether (for example, the transformation of codeine into morphine). <3> The breaking down of a diazo group to originate an amine (for example, the transformation of Prontosilrubrum into sulfanilamide. <4> The transformation of oxazepam in its glucuronide. <5> The transformation of acetylcholine into choline.
Output (English): 2