Final answer:
The type of sporangium that is sessile is the Eusporangium, not the Leptosporangium. Mushrooms fall under the classification of basidiocarps.
Step-by-step explanation:
A type of sporangium that lacks a stalk and is directly attached (sessile) is known as a Eusporangium. The Eusporangium is large, has a broad attachment to the parent plant, and forms from a group of initial cells. In contrast, a Leptosporangium typically develops from a single initial cell, has a stalk (seta), and is less bulky compared to a Eusporangium. Mushrooms produce spores in a structure known as a basidiocarp, which is the fruiting body of basidiomycete fungi. Therefore, mushrooms are classified under the option D. basidiocarp.