Answer :
Answer:
2) C and Cu
Explanation:
Substances that cannot be broken down by chemical means are further known as elements! Therefore, the only valid answers would be ones including only elements.
We can automatically rule out 3 and 4 because CO2 stands for carbon dioxide (a compound!... Not element)
This leaves us with 1 and 2 - Now, 1 includes carbon, but ALSO includes Calcium oxide (a Compound!)
The second option includes C and Cu. These are the element symbols standing for Carbon and Copper!
Hope I was of assistance! #SpreadTheLove! <3