Final answer:
Option 4 is the best choice because it ensures consistent pronoun use by maintaining 'you' throughout the sentence, thereby providing clarity and parallel structure.
Step-by-step explanation:
The ACT English section often tests students on consistency in pronoun usage and maintaining a parallel structure in sentences. When evaluating the sentence 'You should always be on the lookout for new opportunities, but one should also avoid burning bridges if possible', it is important to use the same pronoun throughout for clarity and style.
Option 4, 'You should always be on the lookout for new opportunities, but you should also avoid burning bridges if possible', corrects the inconsistency by using 'you' in both clauses, aligning with the principle of eliminating wordiness and ensuring effective communication.