heating the water before it is frozen adding salt to the water before it is frozen changing the amount of water to be frozen changing the container for the water to be frozen in
I gave my students this multiple choice question: Which action could change the melting point of ice?

Only one answer is correct among these 4 choices:
- heating the water before it is frozen
- adding salt to the water before it is frozen
- changing the amount of water to be frozen
- changing the container for the water to be frozen in

Could you tell me which one is correct?

adding salt to the water before it is frozen