In "shall i compare thee to a summer's day? " shakespeare claims that the object of his sonnet will be immortal because
a. she'll live on in his poem.
b. he'll always love her.
c. she's like the summer's day.
d. she's for all seasons.

The answer is A) She'll live on in his poem.

When Shakespeare said

So long as men can breathe or eyes can see,
So long lives this and this gives life to thee.

he basically stated that as long as someone is reading the poem, the object in the poem will continue to live on.

Example support i believe : )