How Do Amino Acids Like Hydroxylysine and Thyroxine,which Are Not

Multiple Choice

How do amino acids like hydroxylysine and thyroxine,which are not among the 20 amino acids that are inserted into proteins,get into proteins?

A) They are inserted directly.
B) They are the result of the alteration of R groups of the 20 amino acids after their incorporation into the polypeptide.
C) They are the result of the alteration of R groups of the 20 amino acids before their incorporation into the polypeptide.
D) There are more than the 20 amino acids that are said to be inserted into proteins.
E) Their atoms are altered by insertion into the polypeptide.