The correct option is C Columella
The capsule is the terminal part of the sporophyte. The capsule is developed at the apical region of the seta. The capsule is covered by the calyptra. The mature sporophyte of Funaria consists of three different parts:-
(i) Foot (ii) Seta (iii) Capsule
Apophasis is the basal part which is sterile, thin-walled and there are stomata in this region.
Columella is a sterile dome shaped structure responsible for nutrient exchange between active protoplasm below and developing pores inside upper portion of sporangial head.
The annulus is like the plastic ring that holds cans of frozen juice closed; the operculum is like the lid. Once the operculum and annulus have fallen off, the spores can be dispersed.
So, the correct answer is "columella".