Which of the following mixtures can be separated by magnetic separation? 

Method of magnetic separation-  This approach works well when a combination contains material with magnetic characteristics. The magnetic materials are separated using powerful magnets.

Iron filing, sand, and iodine mixture are generally separated using magnetic separation because as we know iron is a magnetic material and will be attracted by a magnet.

The mixture of iodine and salt is not attracted by a magnet.

Common salt, sand, and marble can easily be separated by the hand-making method. 

Winnowing is usually used to remove grain and laugh and then filtration can be used to separate chalk powder.

Filtration and evaporation are commonly used for salt and water solution.

Hence, the correct answer is option A.