Final answer:
The type of sporangium with thin walls is the Leptosporangium, while mushrooms are classified as basidiocarps, the reproductive structure where basidiospores are produced.
Step-by-step explanation:
The type of sporangium that possesses thin walls is B. Leptosporangium. This structure typically develops from a single cell and is found in the true ferns (pteridophytes). Leptosporangia are much smaller than eusporangia and can release spores in a quicker and more efficient manner due to the thinner wall structure that easily breaks open when the spores are mature.
Mushrooms are a type of D. basidiocarp, which is the fruiting body of basidiomycete fungi. Underneath the cap of a mushroom, you can find gills or pores where the basidia produce spores called basidiospores. With proper conditions, these spores will disperse and may germinate to form a new mycelium, thus completing the life cycle of the fungus.