Question: The antitussive dextromethorphan is an enantiomer of the O-methylated derivative of levorphanol that belongs to the structural family of: 
 Options:  <1> 6,7-Benzomorpanos. <2> Morfinanos. <3> 4-Phenylpiperidines. <4> Phenylpropalamine. <5> Oripavinas.
2