The function of the collar cells of sponges is to ____.

A) secrete a matrix that supports the body of the sponge
B) filter and engulf food
C) digest food
D) produce eggs and sperm
E) attach the sponge to a solid surface

The collar cells, also known as choanocytes, are responsible for filtering and engulfing food particles in sponges. They have a flagellum that creates a current to bring in water, and the collar around the base of the flagellum traps food particles. Other options such as secreting a matrix, digestion, producing eggs and sperm, and attachment to a solid surface are all functions performed by other types of cells in sponges.