Answer: A) Layers 1 and 2.
Step-by-step explanation:
Secondary succession refers to when species of plants and animals come back to recolonise an area that was destroyed by a natural disaster of some sort or human activity that change the makeup of the area but somehow left it still capable of supporting life.
As the species that come during secondary succession come after the land has been destroyed so to speak, they would be the later species to arrive which would mean that when they died they would be the closest to the surface when their body decays.
Secondary succession would therefore most likely be observed between layers 1 and 2.