Which piece of evidence best advances the author's purpose of revealing the United States' goal of progress?
O The fair's motto was'Living in the Space Age!" (Hovering Above Seattle
paragraph 2)
O "In the 20th century, St. Louis civic leaders envisioned a memorial that celebrated the city's role in the nation's
westward expansion" (The Gateway Arch. paragraph 1)
O "The city of Seattle designated the Space Needle a historic landmark in 1999
("Hovering Above Seattle"
paragraph 8)
O"They hoped it would breathe new life into the city and become a major tourist attraction. ("The Gateway
Arch, paragraph 1)

C). "In the 20th century, St. Louis civic leaders envisioned a memorial that celebrated the city's role in the nation's westward expansion." ("The  Gateway Arch," paragraph 1)

Explanation:

The piece of evidence which aptly promotes the author's purpose for which he revealed the United States' goal of  progress is 'In the 20th century...expansion' from paragraph 1 of 'The Gateway Arch.' The description regarding the civic leaders of St. Louis planning a memorial that could assist in glorifying the city's significance in the westward expansion of the state/nation substantiates that the author reveals it to convey the readers an idea about the symbolic landmarks that were planned to be created for glorifying the achievements of U.S. Hence, option C is the correct answer.