The answer is H. He is mechanically digesting his food.
the amount of matters refers to the mass
Answer and explanation;
-Aba is a suitable replacement because Aba and Cys have approximately the same sized side chain and are similarly hydrophobic.
-However, Aba cannot form disulfide bonds so it will not be a suitable replacement if these are required.
-Alpha-Aminobutyric acid is biosynthesized by transaminating oxobutyrate, a metabolite in isoleucine biosynthesis.
Answer: "mutations" .
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I am thinking it is by heating themselves in sunlight. I think this because when I bring lizards to mind, they are cold blooded, and they need sunlight to bath in so they do not start to lack warmth to live.
I hope this helps.