Sam,a Deputy Sheriff,stops Two Juveniles Who Are Walking Down the Street

Sam,a deputy sheriff,stops two juveniles who are walking down the street on Halloween night.Sam has responded to a report of minor vandalism in the neighborhood and the two juveniles look like potential suspects.As he is questioning the two,Robert,an attorney,shouts,"Don't say anything kids.No one ever went to jail for remaining silent." The kids heed the advice and refuse to answer Sam's questions.Robert's conduct constitutes:

A) interference with public duties.
B) obstructing a peace officer.
C) resisting arrest or detention.
D) none of the above because he is exercising his right of free speech.