Which is the $C$-terminal residue in glycyl alanine?

Which one of the following statements is correct?

In an amino acid,the carboxylic group ionises at $pH = 2.56$ $(pK_{a_1})$ and the ammonium ion ionises at $pH = 9.38$ $(pK_{a_2})$. The isoelectric point of the amino acid is at:

In which of the following amino acids is the $-OH$ group present?

$(A)$ Lysine	$(B)$ Serine
$(C)$ Tyrosine	$(D)$ Valine

Which of the following is an amphoteric acid?

Which amino acid contains a secondary amino group in its structure?