Answer:
B
Step-by-step explanation:
B is telling you what a stanza is,
While the others are telling you a specific part of the poem that can be included, but not always.
B basically means "a group of two lines together arranged as a unit.", which is a stanza.
A stanza is like a paragraph, a verse in real writing,
but just in a poem.
In summary, it can be all of them, but not always.
More specifically, it is B, because it describes what a stanza literally is.
Hope this helps :)
(My 100th answer!!!!!! TYSM)
-jp524