Final answer:
Tarquinius encountered the gates of Rome closed upon his arrival, and exile was the course of action ordered against him, aligning with the senate's efforts to suppress a conspiracy.
Step-by-step explanation:
When Tarquinius arrived in Rome, based on the given references, the correct answer is D) the gates were closed and exile was ordered. He faced a hostile environment where the Roman senate had taken steps to address a conspiracy by ordering the arrest of certain individuals and forbidding the trading of goods for the purpose of leaving the country. This was part of setting guards at all gates under the orders of the consuls, and making declarations against anyone who might aid fugitives. It reflects a period when the law was stringent against those perceived as threats to the state, requiring them to either face trial or become exiles.