Answer:
So long as men can breathe or eyes can see,
So long lives this, and this gives life to thee.
A Shakespearean sonnet consists of fourteen lines. It is made up of four quatrains (each is four lines) and a couplet, which are always the last two lines. A couplet consists of two lines that rhyme. In this case, the couplet of Sonnet 18 rhymes because of the words "see" and "thee."