Answer
C. Mg
Step-by-step explanation:
When magnesium is in the metallic form it gets burn very easily in air. To start the reaction, the magnesium metal requires a source of energy. The flame provides heat so that the magnesium can overcome their activation energy. Activation energy is the minimum amount of energy needed in the system for a chemical reaction to proceed. Oxygen found in the air forms Magnesium Oxide when the magnesium metal burns in the air. A compound is in which atoms of different elements are linked or bonded to one another. Oxygen and magnesium react to form this compound and forms a white powder of the magnesium oxide that brightens it up.