Which of the following phylum has solenocytes or flame cells as excretory structures?
Solenocyte is a mesoderm-derived elongated cell with a constantly moving long flagellum. The cluster of solenocyte is bathed in the coelomic fluid to facilitate extraction of nitrogenous waste. It constitutes an excretory system of lower invertebrates, for example, Platyhelminthes. Most annelids and molluscs have nephridia which are tubules open at both sides. The inner opening opens into coelom while outer opens outside as nephridiophores. Echinoderms remove waste through the finger-like an extension of coelom called as papulae. Thus, the correct answer is option C.