Which of the following adaptations to life on land is found in both insects and modern reptiles?
a) two pairs of walking legs

b) tracheae to distribute oxygen

c) body surfaces that resist evaporation

d) metamorphosis from a larval form

e) ability to fly

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

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