The line from the poem that leaves readers wondering what makes the speaker realize he should have appreciated his father more is: "What did I know, what did I know."
Before we get to lines quoted from the poem here, we see that the speaker talks about how his father took the pain to drive the cold away from the house and polish his shoes.
Now, when he woke up, he spoke to him indifferently. Thereafter, he asked the question given to show that he did not know what he was doing at that particular time.
Thus, the question shows that he should have appreciated his father's sacrifices more.
Read more about "Those Winter Sundays" at: brainly.com/question/1307975
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