Final answer:
The best Spanish word to complete the sentence is 'cantar'.
Step-by-step explanation:
The best Spanish word to complete the sentence José y Pedro van a esa canción is cantar. The correct sentence is José y Pedro van a cantar esa canción, which means Jose and Pedro are going to sing that song. The word cantar is the correct verb form for the subject pronoun ellos (they) in present tense.
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