(ii) by hand delivery to the occupant of the dwelling unit;
(iii) by enclosure with the January rent bill, if such rent bill is delivered after December fifteenth but no later than January sixteenth; or
(iv) by delivering said notice in conjunction with the annual notice required pursuant to section 17-123 of this code and the rules of the department of health and mental hygiene pertaining to the installation of window guards.
(3) (i) Upon receipt of such notice the occupant shall have the responsibility to deliver by February fifteenth of that year, a written response to the owner indicating whether or not a child of applicable age resides therein. If, subsequent to delivery of such notice, the owner does not receive such written response by February fifteenth, and does not otherwise have actual knowledge as to whether a child of applicable age resides therein, then the owner shall at reasonable times and upon reasonable notice inspect that occupant's dwelling unit to ascertain the residency of a child of applicable age and, when necessary, conduct an investigation in order to make that determination. Where, between February sixteenth and March first of that year, the owner has made reasonable attempts to gain access to a dwelling unit to determine if a child of applicable age resides in that dwelling unit and was unable to gain access, the owner shall notify the department of health and mental hygiene of that circumstance. The department of health and mental hygiene may require by rule that such notification to such department be provided electronically.