Final answer:
The development of the US interstate highway system best fulfilled Cyrus Avery's vision for the future of the United States.
Step-by-step explanation:
The project that best fulfilled Cyrus Avery's vision for the future of the United States is the development of the US interstate highway system. This project, initiated in the 1950s, aimed to connect the nation through a network of high-quality roads. It promoted economic growth, facilitated travel and trade, and enhanced national unity. The interstate highway system transformed transportation and played a crucial role in shaping the modern United States.
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