Final answer:
The poetic device used in Robert Frost's 'After Apple Picking' is enjambment, where line of poetry flows into the next without pause.
Step-by-step explanation:
In the excerpt from Robert Frost's "After Apple Picking," the poetic device used is A. enjambment. This is because the line of poetry continues without a pause onto the next line, allowing for a seamless transition from one thought to the next. Frost's use of enjambment helps to convey the sense of ongoing labor and the never-ending cycle of nature, reflecting the themes common in his poetry that are derived from his observations of New England's natural beauty and everyday situations. This is evident in how the lines 'sticking through a tree / Toward heaven still' do not end with punctuation but rather lead into each other, creating a sense of continuity.