Please paanswer nga po '"":

1.) Cannot be separated

2.) Separates to 2 Hydrogen atoms and an Oxygen atom by Electrolysis

3.) Cannot be separated

4.) Separates to a Carbon atom and 2 Oxygen atoms by Electrolysis

5.) Cannot be separated

Explanation:

2, 3 and 5 cannot be separated into other types of matter because they are ELEMENTS, therefore, pure substances.

number 2 is your answer.