Why are real bath sponges so soft?

A) The silica is dissolved away and only the calcium carbonate remains.
B) The calcium carbonate is dissolved away and only the silica remains.
C) The choanocytes are dissolved away and only the amoebocytes remain.
D) Silica or calcium spicules are removed, leaving only the spongin fibers.
E) The spongin is removed, leaving only the spicules.

Bath Sponges

Natural or synthetic sponges used for cleansing the body; natural ones are harvested from the ocean and belong to a simple, multicellular organism group.

Silica

A hard, unreactive, colorless compound that occurs as the mineral quartz and as a principal constituent of sandstone and other rocks.

Calcium Carbonate

A chemical compound used as a dietary supplement or antacid; it's also the main component of limestone.