These four elements are found in Group 2 of the periodic table, which are alkaline metals, therefore they have the very similar properties because of their 2 valence electrons, which makes them reactive.
Elements in the same group in the periodic table very often show a lot of similarity in physical properties and chemical properties. So in this case, the most probable answer would be D. Magnesium, Calcium, Strontium and Barium are going to share a lot of similar properties that the other group of elements are less likely to share.
