Concept:Pyroclastic means rock fragments and ash thrown out during a volcanic eruption.Explanation:Pyroclastic materials are produced when volcanoes explode and eject broken rock, ash, and volcanic bombs.Deep-sea sediments, desert sands, and river-mouth deposits are formed by other natural processes, not by volcanic ejection.So, pyroclastic best describes fragmented materials that come from volcanoes.Answer:D. fragmented materials ejected by volcanoes