Sedimentary rock indicates the current or past existence of ___.
water
lava
plants and animals
carbon dioxide
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Choose ALL the answers that apply.
The crust is:
the thinnest layer
made of large pieces called plates
mostly made of silicon dioxide
the outermost layer of the earth
also called the hydrosphere
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The ozone layer _____.
is part of the troposphere
is used to send radio signals
protects the earth from UV radiation
is made of charged ions and free electrons
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