Which statement best compares the moon and earth?

they both spin at the same speed.
the moon has carbon dioxide, but earth has oxygen and nitrogen.
they both take the same time to complete one revolution around the sun.
the moon has no atmosphere, but earth has an atmosphere rich in liquid water.

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

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