Answer: The answer is C
Explanation: C and G pair with each other and T pairs with A and A pairs with U
I wanna say it's sand stone but I'm not sure what you are learning about
Bones are made up of Calcium Phosphate given by the chemical formula, 
. When bones are kept in Hydrochloric acid, given by the chemical formula, HCl, they become soft because the calcium compound present in the bones changes its form. The following double displacement reaction takes place when the bones are kept in HCl,
---> 
Calcium chloride is water soluble, and gets washed away. This makes the bone thin and soft.
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