Answer:
The historical progression that demonstrates Winthrop's idea is:
(A) Polk reached an agreement with the British regarding Oregon.
Explanation:
From 1859 to 1872, the United States and Great Britain engaged in a fierce conflict over Oregon. This dispute was sparked by a wayward pig, which led to the US calling it "the Pig War." John Winthrop had previously claimed that the US, representing New England, was destined to be "a city on a hill," evident to all. Gaining control of new territory was seen as aligning with divine will. Not fulfilling the human side of the promise would leave the nation open to mockery. President Polk's unsuccessful efforts in the Pig War against Great Britain regarding Oregon symbolized a failure to maintain the covenant. The conclusion of the war with a treaty, which ceded Vancouver entirely to Britain and Oregon to the US, exposed the country to embarrassment.