Pinacocytes are
A. Ectodermal
B. Mesodermal
C. Endodermal
D. Interstitial cells

Hint: The pinacocytes are flat cells which are found on the outermost layer that is pinacoderm of a sponge. The pinacocytes line the canals and spongocoel. With the help of expansions and contractions, pinacocytes maintain the structure of the sponge.

Complete step by step answer:
The pinacocytes contain many granules.
It helps in maintenance of the size and structure of sponge.
The choanocytes are also body cells of sponges.
The choanocytes have flagella bt pinacocytes do not have flagella.
Sponges are of the phylum porifera.
The sponges are multicellular organisms that have pores in the body which helps in water circulation.
The pinacocytes give shape to sponge.
The ectodermal cells are the cells that form the outer layer of the body wall. The pinacocytes form the outer layer of the body wall of sponges
The organisms of the phylum porifera have pinacocytes, mesenchyme cells and choanocytes.
Pinacocytes can contract which can change the shape of some sponges.
The pinacoderm is composed of pinacocytes.
There are three types of pinacocytes- basipinacocytes , exopinacocytes and endopinacocytes.
So the correct answer is ectodermal.

So the correct answer is C.

Note: The mesodermal cells form the middle layer of the body wall. The endodermal cells form the inner layer of the body wall. The most important structure in the sponges is a system of canals and chambers by which water circulates to bring food and oxygen to the sponge.