Or, eligibility could be restricted to those who have already been pregnant, or at least sexually active; to those over age 13, or under age 21; or some combination thereof.
( Or ( , ( eligibility ( ( could ( be ( restricted ( ( ( ( ( ( to ( those ( who ( ( have already ) ( been ( ( ( ( pregnant , ) or ) ( at least ) ) ( sexually active ) ) ) ) ) ) ) ; ) ( to ( those ( over ( age 13 ) ) ) ) ) , ) or ) ( under ( ( ( ( age 21 ) ; ) or ) ( some ( combination thereof ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (CC Or) (, ,) (NP (NN eligibility)) (VP (MD could) (VP (VB be) (VP (VBN restricted) (PP (PP (TO to) (NP (NP (DT those)) (SBAR (WHNP (WP who)) (S (VP (VBP have) (ADVP (RB already)) (VP (VBN been) (NP (NP (JJ pregnant)) (, ,) (CC or) (ADVP (IN at) (JJS least)) (NP (RB sexually) (JJ active))))))))) (: ;) (PP (TO to) (NP (NP (DT those)) (PP (IN over) (NP (NN age) (CD 13))))) (, ,) (CC or) (PP (IN under) (NP (NP (NN age) (CD 21)) (: ;) (CC or) (NP (DT some) (NN combination) (RB thereof)))))))) (. .)))
Eligibility is restricted to those over age 13, quite possibly.
( Eligibility ( ( is ( restricted ( to ( those ( over ( ( ( age 13 ) , ) ( quite possibly ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Eligibility)) (VP (VBZ is) (VP (VBN restricted) (PP (TO to) (NP (NP (DT those)) (PP (IN over) (NP (NP (NN age) (CD 13)) (, ,) (NP (RB quite) (RB possibly)))))))) (. .)))