Actually, you've got two (2) incomplete sentences that need best word or phrase to be complete: "<em>Caesar Augustus made sure that the central government controlled </em><u><em>tax collection</em></u><em>.</em>" "<em>Engineers built the </em><u><em>Field of Mars</em></u><em>, which had government offices and statues.</em>"
Thus, the correct answers are "tax collection" and "Field of Mars".
The third sentence is already complete: <em>"A </em><em>mail service</em><em> was created to improve communication." </em>
Also, the last sentence: <em>"Caesar Augustus ordered the construction of </em><em>aqueducts</em><em>, which improved water supplies and provided water for crops." </em>is also complete.
These matters fall under the topic "Roman Empire: At Its Height," and they primarily concern Caesar Augustus.
Learn about Caesar Augustus's main reason for ordering the construction and renovation of buildings in Rome: brainly.com/question/15641074
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It was set at the Mississippi river, hope this helps
