Why does duncan feel he is guilty of ingratitude toward macbeth

Which punctuation mark would best fill in the blanks in the following sentence in the past year i visited denver, colorado portland oregon and seattle washington

That time of year thou mayst in me behold when yellow leaves, or none, or few do hang upon those boughs which shake against the cold, bare ruined choirs, where late the sweet birds sang in me thou sees the twilight of such day as after sunset fadeth in the west; which by and by black night doth take away, death's second self that seals up all in rest. in me thou seest the glowing of such fire that on the ashes of his youth doth lie, as the deathbed whereon it must expire, consumed with that which it was nourished by. this thou perceiv'st, which makes thy love more strong, to love that well, which thou must leave ere long. the first stanza compares the leafless limbs of a tree to a.yellow leaves b.sweet birds c.bare choirs d.summer

What is meant by “eternally burning black pipes”? what is this implying about the personality of the firemen?