Final answer:
To agree the infinitive with the indicated subjects in Spanish, the form of the verb must change according to the subject. For example, 'cantar' changes to 'canto' for 'yo' and 'canta' for 'María'.
Step-by-step explanation:
(a) To canto una canción.
(b) María canta una canción.
(a) Llevamos zapatos.
(c) Tú cantas una c.
(d) Vds. cantan una
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