Alrighty, so:
Anterior- Referring to the head end of a bilaterally symmetrical animal.
Posterior-Of or pertaining to the rear, or tail, end.
Medial- Most likely means middle.
Ventral-Pertaining to the undersurface of an animal that holds its body in a horizontal position; to the front surface of an animal that holds its body erect.
Knowing these things I think of the sentence as:
"Make an incision down the middle of the belly from top to bottom."
Therefore I think the answer is A.)Make an incision on the front in the middle from top to bottom.
(It's been a very long time since I took Biology. I hope I'm correct.)
Hope this helps! (: