Essential amino acids are those that cannot be synthesized by the body and must be obtained from the diet.
Let's examine the given amino acids:
(i) Leucine – Essential amino acid.
(ii) Glutamic acid – Non-essential amino acid.
(iii) Asparagine – Non-essential amino acid.
(iv) Valine – Essential amino acid.
Thus, the correct answer is option D, as Leucine and Valine are essential amino acids.