Question

how does the structure of this sonnet most clearly affect its meaning and style?
its regular pattern of rhythm, or meter, reflects the progression of one season to the next.
it has fourteen lines, which suggests the theme that the passage from youth to old age is brief.
it has a group of lines without stanza breaks, which matches the image of \solid tree trunks\ in the poem.
its rhyme scheme departs from a sonnets usual pattern in order to imitate the uniqueness of the birds song.

Explanation:

A sonnet typically has a regular meter. A regular rhythm or meter can symbolize order and progression, like the progression of seasons. A sonnet has 14 lines, but 14 lines don't inherently suggest the brevity of youth - to - old age passage. A sonnet usually has a defined structure (often with stanzas like three quatrains and a couplet), so a group of lines without stanza breaks is not a typical sonnet structure related to "solid tree trunks". A sonnet has a traditional rhyme scheme (e.g., Petrarchan or Shakespearean), and departing from it for the uniqueness of a bird's song is not a common sonnet - structure - meaning connection.

Answer:

Its regular pattern of rhythm, or meter, reflects the progression of one season to the next.