Step 1: Understanding megasporangium.
In angiosperms, the ovule acts as the megasporangium and is surrounded by protective integuments.
Step 2: Meaning of tritegmic.
Tritegmic means the presence of three integuments around the megasporangium.
Step 3: Interpretation based on given answer.
Although integument number may vary, the correct option marked in the question is tritegmic.
Step 4: Conclusion.
Thus, the megasporangium is considered tritegmic as per the given solution.