Answer:
D. water undergoing electrolysis
To help, I drew a diagram. This represents an ionic bond between Na and Cl. Na is giving his single electron to Cl, which is indicated by the arrow, to make Cl full with 8 electrons.
60% are active all the time.
Answer:
combustion of methane gass will take place when the flame is yellow
For Iron:

For Oxygen:

These are the two chemical symbols for the two elements found in Iron Oxide.