shake the mixture until the sand settles on the bottom pour the mixture through the filter paper heat the mixture on the hot plate dissolve the salt by adding water to the mixture
I gave my students this multiple choice question: A group of science students used water, filter paper, and a hot plate to separate a mixture of salt and sand. Which of the following did the students most likely do first?

Only one answer is correct among these 4 choices:
- shake the mixture until the sand settles on the bottom
- pour the mixture through the filter paper
- heat the mixture on the hot plate
- dissolve the salt by adding water to the mixture

Could you tell me which one is correct?

dissolve the salt by adding water to the mixture