The sequence of ionic mobility in aqueous solutions is -

Question

( A ) $K^+$ > $Na^ +$ > $Rb^+$ > $Cs^+$
( B ) $Rb^ +$ > $K^+$ > $Cs^+$ > $Na^+$
( C ) $Na^ +$ > $K^+$ > $Rb^+$ > $Cs^+$
( D ) $Cs^+$ > $Rb^ +$ > $K^+$ > $Na^+$