Body of Euspongia is mainly composed of
A) Spicules
B) Spongin fibres
C) Mesogloea
D) Nematoblasts

Hint: Sponges belong to phylum Porifera. These are marine sponges present in the family spongiidae which was formerly depicted by Carl Linnaeus in 1759. This family consists of more than 60 species. These sponges are often utilized as a cleaning tool and also as an absorbent substance in surgeries.

Complete answer:
Sponges belonging to phylum Porifera are included in the class Demospongiae. These are diploblastic animals without true body cavity. They are also known as bath sponge and moreover, this sea sponge is used for commercial purposes. It can be found all through the Mediterranean Sea. These sponges can reproduce both sexually and asexually. They carry out asexual reproduction through fragmentation or budding. Moreover, these are hermaphrodites and can reproduce sexually via production of sperms and oocytes. Their body skeleton chiefly comprises spongin fibers.
On the other hand, sponges belonging to class Calcarea have calcareous spicules while the sponges belonging to class Hexactinellida consists of siliceous spicules.
However, mesoglea which is also known as mesenchyme, is a matrix formed of protein and gelatin. It serves as an interconnection between the inner and outer layer of the body wall of sponges.

So the correct answer is option “B” that is the body of Euspongia is mainly composed of spongin fibres.

Note: Sponges are generally globular in shape. It is mainly found attached to the substratum in shallow waters. The dried skeleton of these sponges is often used as bath sponge therefore they are also known as bath sponges.