Be shows diagonal relationship with (a) Mg (b) Al (c) B (d) Na

Diagonal relationship between two elements in the periodic table means that they have similar chemical and physical properties. In the case of Be and Mg, they have a similar atomic radius, electronegativity, and reactivity. Al, B, and Na all differ from Be in terms of atomic radius, electronegativity, and reactivity, so they do not have a diagonal relationship.