What is the rhyme scheme of four-line stanza?

There's no single rhyme scheme for a four-line stanza. A stanza can have many different rhyme schemes, here are some common ones:

* AABB: Lines 1 and 2 rhyme, and lines 3 and 4 rhyme.

* ABAB: Lines 1 and 3 rhyme, and lines 2 and 4 rhyme.

* ABBA: Lines 1 and 4 rhyme, and lines 2 and 3 rhyme.

* AAAA: All four lines rhyme.

* ABCB: Lines 1 and 3 rhyme, and lines 2 and 4 rhyme.

Additionally, there are free verse stanzas which don't have a set rhyme scheme.

To determine the rhyme scheme of a specific four-line stanza, you need to look at the words at the end of each line and see if they rhyme.