I believe that's informal writing.
Okay, so this is a little hard to answer when you do not have the excerpts, but I will try my best to work a answer out of the headings. I think your answer would be C. It makes sense, the info that comes after the titles, so If I were you I would go with C.
I hope that helps.
To rest or move on or near the surface of a liquid without sinking.
