A seaman needs to join two lines of unequal diameter under moderate strain. Which knot or bend is most appropriate for this task?

Why C is correct

NAVEDTRA 14067 §3-2 identifies the sheet (becket) bend as the correct choice for joining two lines, especially of unequal size, and states it holds better than a square knot. The square knot is not trusted for joining lines under strain, the bowline forms an eye rather than joining two lines, and the clove hitch secures a line to a spar.