Final answer:
The word 'acaban' best completes the sentence 'de terminar el programa'.
Step-by-step explanation:
The word 'acaban' best completes the sentence 'de terminar el programa'. 'Acaban' is the correct form of the verb 'acabar' in the third-person plural, present tense. It matches the subject 'ellos', which means 'they' in Spanish. This form of the verb indicates that the action of finishing the program is being done by the subject 'ellos'.
Learn more about Spanish verb conjugation