is fully or currently insured (as such terms are defined in section 414 of this title ), or would be fully or currently insured if (i) his service as an employee (as defined in the Railroad Retirement Act of 1974 [ 45 U.S.C. 231 et seq.]) after December 31, 1936 , were included within the meaning of the term “employment” for purposes of this subchapter, and (ii) his medicare qualified government employment (as defined in section 410(p) of this title ) were included within the meaning of the term “employment” for purposes of this subchapter;

(i) is entitled to monthly insurance benefits under this subchapter, (ii) is entitled to an annuity under the Railroad Retirement Act of 1974 [ 45 U.S.C. 231 et seq.], or (iii) would be entitled to a monthly insurance benefit under this subchapter if medicare qualified government employment (as defined in section 410(p) of this title ) were included within the meaning of the term “employment” for purposes of this subchapter; or

is the spouse or dependent child (as defined in regulations) of an individual described in subparagraph (A) or (B);