Section 5. Said petition may be served by the sheriff of the county, or by the sheriff of any other county specially deputized for that purpose, upon the respondents named therein-
(a) by handing an exact copy thereof to each of them personally, or
(b) by leaving an exact copy thereof at the residence of each of them with an adult member of his family, or
(c) if service cannot be had in either of the above methods, and the return of the sheriff is that the respondent or respondents or any of them cannot be found in this county or state, said respondent or respondents may be served by publishing in the legal newspaper of the county, and one newspaper of general circulation in the county, at least ten days prior the the presentation of such petition, a notice to the said respondent or respondents of the filing of said petition and of the time and place fixed for hearing thereon: Provided, however, That if there be no legal newspaper in the county, then in one newspaper of general circulation in said county.