A, the cuticle is used for water conservation.
By mutation over time of RNA chains
Both humans and monkeys have this. A VERY long time ago Humans had very small "strings" of skin. This skin has evolved over time and now there is a bone left. Monkeys are technically un-evolved humans. Good thing they stuck around.
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Answer is 3 it uses chemical and physical changes when using stomach acid and physical when turning food in your stomach.