A. Acting as a net in a current that sweeps food particles through it. B. Squeezing the spongocoel cavity and sucking debris in and out through the osculum. C. The beating of the flagella of collar cells, forming a current; food is absorbed by collar cells. D. The beating collar cells form a current from osculum to pores; the food is engulfed by amoebocytes in the central cavity of the sponge.