Answer:
A. Compounds contain fixed ratios of different elements.
Explanation:
Water always has this 2:1 ratio of hydrogen to oxygen. Like water, all compounds consist of a fixed ratio of elements. It doesn't matter how much or how little of a compound there is. It always has the same composition.
Atmosphere.
Hydrosphere.
Biosphere.
Cryosphere.
Lithosphere(also referred to as the Geosphere).
Quick Answer. Collagen is the protein that all animals have in common, even single-celled animals and creatures such as sponges that lack differentiated bodies. Collagen is a cable-like protein that can calcify into bone, shell or other hard structures.
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