(A) is true, (R) is true and (R) is the correct explanation for (A).

(A) is true, (R) is true but (R) is not the correct explanation for (A).

(A) is true but (R) is false.

(A) is false but (R) is true.

A, B and C only

A, C and D only

C and D only

A, B, C and D

$\mathrm{Mg}^{2+}<\mathrm{Na}^{+}<\mathrm{F}^{-}<\mathrm{O}^{2-}$

$\mathrm{Mg}^{2+}<\mathrm{F}^{-}<\mathrm{Na}^{+}<\mathrm{O}^{2-}$

$\mathrm{O}^{2-}<\mathrm{F}^{-}<\mathrm{Na}^{+}<\mathrm{Mg}^{2+}$

$\mathrm{O}^{2-}<\mathrm{Mg}^{2+}<\mathrm{F}^{-}<\mathrm{Na}^{+}$

$\mathrm{Na}^{+}>\mathrm{Al}^{3+}>\mathrm{Mg}^{2+}>\mathrm{K}^{+}$

$\mathrm{K}^{+}>\mathrm{Na}^{+}>\mathrm{Mg}^{2+}>\mathrm{Al}^{3+}$

$\mathrm{K}^{+}>\mathrm{Na}^{+}>\mathrm{Al}^{3+}>\mathrm{Mg}^{2+}$

$\mathrm{Al}^{3+}>\mathrm{Mg}^{2+}>\mathrm{K}^{+}>\mathrm{Na}^{+}$