Final answer:
The correct form of the future tense in Spanish for the sentence 'Después de la fiesta, ustedes estarán cansados.' is 'estarán'
Step-by-step explanation:
The correct form of the future tense for the sentence 'Después de la fiesta, ustedes estarán cansados.' is estarán.
This form is used to indicate an action that will happen in the future. In this case, it is stating that after the party, 'ustedes' (which means 'you all') will be tired.
Other forms of the future tense in Spanish include 'estaré' (I will be), 'estaremos' (we will be), etc.
Learn more about Spanish verb conjugation