Answer:
Echinoderms have a calcium carbonate endoskeleton, and vertebrates have a bony endoskeleton made of calcium phosphate. have bones mostly made of calcium phosphate.
Explanation:therefore, echinoderms do not have true endoskeletons.
Solar energy is a form of renewable energy, namely energy that cannot be depleted. Other forms of energy like carbon based sources of energy cannot be renewed in a reasonable span after being used (forests take time to grow and oil is created in geological timescales). Joe is trying to deal with the phenomenon of resource depletion. The way he goes about it is making a renewable source of energy more efficient and usable.
I’m not sure but I’m guessing the answer would be the first one !
