Free SAT Practice Question

The following text is adapted from Emily Dickinson's poem "A Day," first published in 1890.

I'll tell you how the Sun rose—
A Ribbon at a time—
The Steeples swam in Amethyst [a gem]—
The news, like Squirrels, ran—
The Hills untied their Bonnets—
The Bobolinks [a bird]—begun—
Then I said softly to myself—
"That must have been the Sun!"

But how he set—I know not—
There seemed a purple stile
That little Yellow boys and girls
Were climbing all the while—
Till when they reached the other side,
A Dominie [a pastor] in Gray—
Put gently up the evening Bars—
And led the flock away—

Which choice best describes the overall structure of the text?