Final answer:
Brutus was concerned about the threat to individual freedoms in a large republic, aligning with option (a) regarding centralization in a large republic.
Step-by-step explanation:
Brutus, a pseudonymous Anti-Federalist writer, was concerned about the potential threat to individual freedoms in a large republic. He belonged to the group that feared that a large federal republic might lead to a loss of common interests and virtues. In contrast to Federalists, who supported a strong central government as a defense against tyranny, Brutus and the Anti-Federalists were wary of centralization and its implications for personal liberties and democracy at a local level. This aligns with option (a) of the multiple-choice question posed.