Answer : The correct option is, screening
Explanation :
There are various methods for separation of mixture.
Magnetism : It is a method of separation in which the components of the mixtures separated by using the magnets to attract magnetic materials. For example : iron and sand mixture
Filtration : It is a method or separation in which the insoluble solid separated from the liquid by using porous material. For example : sand and water mixture
Screening : It is a method of separation in which the mixture is separated on the basis of the particle size. For example : sand and stone mixture
Separation by density : It is a method of separation in which the mixture is separated when the substance are in different phase. For example : oil and water mixture
As per given mixture of sand and stone, the screening method is used for their separation because the different particle size.
Hence, the best method used to separate the given mixture of sand stone is, screening.
