i want to say it is D. because i believe that they are nocturnal animals and they are found in deserts.
"The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period, 419.2 Mya.<span> <span>Wikipedia."
https://www.google.com/search?q=He+Silurian+period+occurred&rlz=1C1RUCY_enUS760US760&oq=He+Silurian+...
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The process that is responsible for the formation of a normal fault is
when horizontal stresses occurs in brittle rocks and the hanging wall blocks moves down relative to the footwall blocks
hope this helps
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