a candle burning a shoelace being tied a pipe being cut in half a block of ice melting
I gave my students this multiple choice question: Which example shows a new substance being formed?

Only one answer is correct among these 4 choices:
- a candle burning
- a shoelace being tied
- a pipe being cut in half
- a block of ice melting

Could you tell me which one is correct?

a candle burning