The correct answer is Beryllium (Be).
Magnesium (Mg) belongs to the alkaline earth metals (IIA elements) of the periodic table.
Similarly Beryllium (Be) belongs to the alkaline earth metals (IIA elements) of the periodic table.
Since both Magnesium (Mg) and Beryllium (Be) belong to alkaline earth metals (IIA elements), they will have most properties in common with each other.
Sodium (Na) belongs to the alkali metals (IA elements) of the periodic table.
Aluminum, a member of the IIIA family, belongs to p-block of the periodic table.
Manganese (Mn) belongs to the transition elements of the periodic table.