Task: Text Categorization
Input (English): Question: The antitussive dextromethorphan is an enantiomer of the O-methylated derivative of levorphanol that belongs to the structural family of: 
 Options:  <0> 6,7-Benzomorpanos. <1> Morfinanos. <2> 4-Phenylpiperidines. <3> Phenylpropalamine. <4> Oripavinas.
Output (English): pharmacology