Here's a problem to solve: A teacher is conducting an investigation by using special equipment to hold a magnesium (Mg) ribbon over the flame of a Bunsen burner. Which observation indicates a chemical reaction took place?

Among the 4 following options, which is the correct answer?

- A: The temperature of the magnesium ribbon increased.
 
- B: The shape of the magnesium ribbon changed.
 
- C: The burning magnesium produced light.
 
- D: The magnesium appeared to evaporate.
 