Hint: Slime mould or slime moulds are an informal name given to many types of eukaryotic non-related species that can live freely as single cells but can form multicellular reproductive structures together. Formerly known as fungi, slime moulds are no longer considered part of that kingdom.
-Elaters: An elater is a hygroscopic cell that will change its shape in response to environmental moisture changes. Elaters come in a number of types, but they are often related to plant spores. Elaters are present in bryophytes and assist in spore dispersal. Hence option A is incorrect.
-Pseudoelaters: Pseudo-elaters are small, filamentous structures which in many liverwort species superficially resemble the spiral elaters that are a feature of the capsules. In the genus Anthoceros, these pseudo-elaters do not spiral and assist in the release of spores. Hence option B is incorrect.
-Capillitium: The fruiting body of slime moulds contains Capillitium. They are sterile filaments and they are active in spore dispersal. Hence option C is correct.
-Capitulum: The primary inflorescence contained in the Compositae, sometimes referred to by the layman as a flower while seeing a traditional radiate capitulum, and often in many texts ahead, is composed of an involucre of defensive bracts covering the florets around the receptacle (the phyllaries). Hence option D is incorrect.
Hence option C: capillitium is the correct answer.
Note: The existence of capillitium characterises slime moulds. It is a branched sterile fibre system that is found within the fruit body. In some bryophytes, elaters and pseudoelaters occur, whereas capitulum is a form of the inflorescence.