They are like that because they can't always be faulty and may have at least some spark of truth to this theory also as stated earlier a theory in scientific terms is just an observation so it can't really be turned down hence theory.
The answer will be to: produce protein
The correct answer for this question is D - lipids. Lipids are also
known as fat, and are useful not only as protection, but also as long
term storage for energy, protection for vital organs. A certain type of
lipid even assists with communication between cells.
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