Answer:
She could prove that it is a combination of substances by looking for a change in color, or the formation of bubbles. She could also try to pull the combination apart by physical means alone.
Explanation:
After that have been up for a while thay are metal
Answer:
C2H4 + 3O2 --> 2CO2 + 2H2O
Explanation:
For an equation to be balanced, it must have an equal number of atoms on each side. C2H4 + 3O2 --> 2CO2 + 2H2O is the only equation out of these four the fulfills this requirement.