Please help- im failing this subject and this is the last retake- i dont really want my asz beat today so please answer quickly i have 20 more minutes, im timed- ill do anything i possibly can if you actually help- i dont have many points.
Which of the following correctly identifies the most productive layer of a soil profile?

topsoil, just below undecomposed organic matter

parent material, just above bedrock

undecomposed organic matter, at the very top

subsoil, between topsoil and parent material