Answer:
D. It compares the smith's muscles to iron to show their firmness.
Step-by-step explanation:
A simile is a figurative language that compares things alike with the use of the comparing word "as" or "like". This direct comparison allows for the similarities to be highlighted in a much better and understandable way.
In the given poem "The Village Blacksmith" by Henry Wadsworth Longfellow, the simile is used in the last line of the first stanza where the poet comments "the muscles of his brawny arms / Are strong as iron bands". The poet compares the muscles of the smithy to that of iron bands.
Thus, the correct answer is option D.