Final answer:
The correct conjunction to complete the sentence is 'pero', which means 'but' in Spanish.
Step-by-step explanation:
The correct conjunction to complete the sentence is pero.
The sentence translates to: The dry cleaner's is open, but I don't have time to drop off the clothes today. I will take them tomorrow.
The word pero means 'but' in Spanish and is used to contrast two ideas or actions.
Learn more about Conjunctions in Spanish