I looked it up and I got fungi which isnt one of your answer choises the best I can do is tell you its either A or B I think.
Answer:
I'd say an exoskeleton.
Explanation:
My main reason for saying this is because bugs with exoskeletons survive much better than bugs with endoskeletons or (surprise surprise) no skeletons. If your skeleton is outside your body, it protects everything inside you. Endoskeletons merely help hold you together.
Over a millions of years of animals and plants being crushed down in the ground<span />
