Answer:
c. Cr
Explanation:
The compound is containing 
ion.
If acid reacts with it, CO_2 evolves.
therefore, Cr would form a precipitate when added to an aqueous solution of this compound. Cr2CO3 is the precipitate.
The chemical formula is
composed of hydrogen and oxygen where the two atoms are bonded through hydrogen
bond type of bonding. In this pair, the oxygen is the more electronegative atom
hence the electrons are more directed to it. Because of this, this creates
electron polarity which affects the chemical property of water.
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Answer:
2 examples are cardiovascular and respiratory systems.
