In which horizons would plant be planted

It is important to mention that "horizon" make reference to each layer that the soil has. Each of them has different characteristics which allow them to fulfill different roles. 
 If you want to plant the most appropriate horizon would be A. (A horizon) This is made up of mineral and decomposed matter and it presents a dark color. here many plats roots grown in.

Ihaven't done that yet, so no idea,but this is not the right place to ask

Ithink the answer is c. i’m not sure though i’ll notify you when i have an exact answer!