D. None of these!
The additional information contained on the bottom of a paper is called footnote.
We can add it as an observation or complementing reference that doesn't get in the middle of the text disturbing the reading flow. It may help to show the source of our information or to complete an idea for better understanding, that can be read later. We may find footnotes on academical works, newspapers, some versions of the Bible and in other types of works.
