using a magnet to extract the salt adding a colored dye to the mixture pouring the mixture through a filter boiling the mixture until the water evaporates
I gave my students this multiple choice question: Which action is the best method to separate a mixture of salt and water?

Only one answer is correct among these 4 choices:
- using a magnet to extract the salt
- adding a colored dye to the mixture
- pouring the mixture through a filter
- boiling the mixture until the water evaporates

Could you tell me which one is correct?

boiling the mixture until the water evaporates