Arthropod exoskeletons and mollusc shells both arthropod exoskeletons and mollusc shells both completely replace the hydrostatic skeleton retain moisture in terrestrial habitats are comprised of the polysaccharide chitin are secreted by the mantle

The correct answer is that they help to retain moisture in terrestrial habitats.

Arthropods exoskeletons and mollusk shells both help to retain moisture in the terrestrial habitats.

Arthropod is an invertebrate animal which have an exoskeleton, paired jointed appendages and segmented body. They are characterized by their jointed limbs which are cuticle and are made of chitin.

They are the most species-rich members of all ecological guilds in most environments.

Molluscs are termed as large phylum which is of invertebrate animals. They are the largest marine phylum and they live in terrestrial habitat and freshwater.

a bird that nests only in a particular tree species.

the statements that apply here about binary star system are

"have stars that might appear to wobble"

"often have one star that is brighter than other"

a binary star is a star system consisting of two stars revolving around their common barycenter. systems of two or more stars are called multiple star systems.