So, I said, No, I said, I'm not going to be able to go.
( So ( ( , ( ( I ( ( said , ) ( No ( , ( I said ) ) ) ) ) , ) ) ( I ( ( ( 'm not ) ( going ( to ( be ( able ( to go ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB So)) (PRN (, ,) (S (NP (PRP I)) (VP (VBD said) (, ,) (S (INTJ (UH No)) (, ,) (NP (PRP I)) (VP (VBD said))))) (, ,)) (NP (PRP I)) (VP (VBP 'm) (RB not) (VP (VBG going) (S (VP (TO to) (VP (VB be) (ADJP (JJ able) (S (VP (TO to) (VP (VB go)))))))))) (. .)))
I could not go because I had to study for an exam.
( I ( ( ( could not ) ( go ( because ( I ( had ( to ( study ( for ( an exam ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (MD could) (RB not) (VP (VB go) (SBAR (IN because) (S (NP (PRP I)) (VP (VBD had) (S (VP (TO to) (VP (VB study) (PP (IN for) (NP (DT an) (NN exam))))))))))) (. .)))