Concept:Poetic forms are often classified by their fixed number of lines.Explanation:A sonnet is a poem that contains exactly 14 lines.This is its defining feature in poetry.The other options do not match this length.An octave is a verse unit of 8 lines.A sestet contains only 6 lines.A quatrain is made up of 4 lines.Therefore, the term that correctly describes a poem of 14 lines is "sonnet".Answer:A. sonnet