The correct option is D Annulus
During the early stages of development, the sporophyte is completely surrounded by a tough protective covering called as the calyptra. When the sporophyte is mature, the calyptra is shed and the capsule is revealed. At the tip of the capsule is a lid (operculum) which, prior to spore dissemination, falls away exposing the so-called peristome teeth, a set of structures, often delicate and thread-like in appearance, that form a ring around the mouth (rim) of the capsule. The dehiscence of moss capsule takes place by rupture of the annulus.
Endothecium tissue found in moss capsules functions in a similar way in dehiscence to the endothecium in the walls of anthers. Many leptosporangiate ferns have an annulus around the sporangium, which ejects the spores. Eusporangiate ferns do not generally have specialized dehiscence mechanisms.