Which quotation from a shakespearan sonnet is a couplet

The Shakespearean sonnet has the rhyme scheme ABAB CDCD EFEF GG, forming three quatrains (four lines in a group) and a closing couplet (two rhymed lines). The problem is usually developed in the first three quatrains, each quatrain with a new idea growing out of the previous one.

sonnet 18 no 4

"So long as men can breathe or eyes can see,

So long lives this, and this gives life to thee."