(a) Every assistance unit must include a child, except as provided in subsections (b) and (c). The child or children must have already been born and be under age 18, or, if age 18, must be a full-time student in a secondary school or the equivalent level of vocational or technical training.
     (b) Grants shall be provided for assistance units consisting exclusively of a pregnant woman with no dependent child, and may include her husband if living with her, if the pregnancy has been determined by medical diagnosis.
     (c) Grants may be provided for assistance units consisting of only adults if all the children living with those adults are children with disabilities and receive Supplemental Security Income.