Final answer:
The Achaemenid (Persian) Empire was successful because it honored local customs and religions of conquered nations and granted their citizens certain freedoms, so long as those citizens remained loyal and fulfilled their obligations to the empire. so, option a is the correct answer.
Step-by-step explanation:
The success of the Achaemenid (Persian) Empire among its conquered nations is often attributed to their policy of honoring local customs and religions, while granting certain freedoms to their subjects. This approach was indeed a major innovation for the time and starkly contrasted with the more oppressive regimes of the Assyrians and Neo-Babylonians. The Persian Empire rulers, such as Cyrus the Great, allowed a high degree of autonomy, permitting local languages, religious practices, and trading customs to continue largely uninterrupted. This was done as long as the conquered peoples remained loyal, paid their taxes, and provided troops when necessary.
Consequently, the policy fostered a multiethnic, multilingual, and multireligious society under a centralized bureaucracy. The Persians even employed indigenous languages and administrative structures in the lands they conquered, exemplified by the retention of hieroglyphic script in Egypt and traditional Babylonian record-keeping in Mesopotamia.