Final answer:
The correct conjunction to complete the sentence is 'sino' meaning 'but'
Step-by-step explanation:
The correct conjunction that best completes the sentence 'Pablo son peluqueros. Juan' is 'sino'. 'Sino' is used to introduce an alternative or contrasting idea, implying that Juan is not a hairdresser like Pablo. For example, you could say 'No es Juan un peluquero, sino un estilista' (Juan is not a hairdresser, but a stylist).
Learn more about Conjunctions in Spanish