Spongocoel in general, is lined by
(a)Double layer of pinacocytes
(b)Single-layer of pinacocytes
(c)Single-layer of choanocytes
(d)Double layer of choanocytes

Hint: The cells having flagella with the protoplasm that are also called collar cells and they sometimes made a thin layer.

Complete answer:
Spongocoel is a large, central cavity of sponges from where water enters. The spongocoel is surrounded by a lining of cells called choanocytes, containing a central flagellum that is surrounded by microvilli.

Additional Information:
-The spongocoel consists of many tiny pores called Ostia from where water enters and the exit point is a large opening called the osculum.
-The spongocoel can be a simple inner space or branched complex inner structure.
-The body of the spongocoel is lined by choanocytes having flagellum which helps in pushing water through the spongocoel.
-The spongocoel varies in its simplicity and complexity depending upon its body plant which can be; Asconoid 9simplest body organization having pores for passage of water), syconoid (tubular body having choanocytes lining with the thicker wall), and leuconoid (complex body organization with branched canal system).
-There are various types of cells by which spongocoel are lined
Porocytes – These cells line the pores of the sponge. By these cells, water is taken into the organism.
Amoebocytes – they have flagellum which creates inward water currents.
Choanocytes -According to the body plan, spongocoel has a various lining, they are: on the surface of the spongocoel (asconoid sponges), radial canals in syconoid sponges, and chambers like in leuconoid sponges.

So, the correct answer is the ‘Single layer of choanocytes'.

Note: Sponges belong to the phylum Porifera which means pore borer. It is derived from the Greek word meaning sponges. The organisms lack true tissues and organs. They are found in ocean habitats, and rocks. A few of the carnivorous sponges have lost their water system and the lining of choanocytes cells.