Question

while silica is used to make glass, these sea sponges are not actually made of glass. these sponges have a remarkable appearance that is almost \ghostly\ due to their semi - transparent bodies. they are well adapted to deep - sea environments, where they thrive in the absence of sunlight. what material makes up the skeleton of hexactinellid sponges? sand silica calcium carbonate

Explanation:

The text mentions silica is related to these sea - sponges and is used to make glass, though the sponges aren't glass. It implies silica makes up their skeleton.

Answer:

B. silica