putting them in the freezer burning them with a candle cutting them into small pieces mixing them with pieces of copper
I gave my students this multiple choice question: Magnesium strips are long, thin strips that are gray and shiny. Which action will lead to a chemical change of magnesium strips?

Only one answer is correct among these 4 choices:
- putting them in the freezer
- burning them with a candle
- cutting them into small pieces
- mixing them with pieces of copper

Could you tell me which one is correct?

burning them with a candle