The increasing order of pKa of the following amino acids in aqueous solution is Gly Asp Lys Arg

Structure of the given α− amino acids are
${\mathrm{H}}_3\mathrm{N}-{\mathrm{CH}}_2-{\mathrm{COO}}^{-}$ Glycine(Gly)

Here, aspartic acid is acidic, glycine is  neutral, while lysine and arginine are basic amino acids. Also, arginine is more basic due to stronger basic functional groupd 
$\therefore$The order of pK_a value is directly proportional to the basic strength of amino acids, thus Arg > Lys > Gly > Asp