The correct answer is - they all contain three quatrains and a couplet.
The structure of all of Shakespeare's sonnets is the same - all of them contain three quatrains and a couplet. A quatrain is a stanza consisting of 4 lines, and a couplet contains 2 lines. So in total, a Shakespearean sonnet consists of 14 lines. The couplet is the most important part of the poem - it is the explanation and the main theme of the entire sonnet.
A quatrain is a stanza of four lines with an alternating rhyme scheme. A
couplet is a set of two lines that rhyme and are treated as a set.
Shakespeare's sonnets all contain three quatrains and one couplet.
