Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. The regularity and power of stone walls inspired Romans attempting to unify the parts of their realm. B. Although the Romans used different types of designs when building their walls, they used regular controls to maintain their realm. C. Several types of control united the Roman realm, just as design and cement held Roman walls together. D. Romans built walls to unite the various parts of their realm into a single entity, which was controlled by powerful laws.