A Codon That Specifies the Amino Acid Ile Undergoes a Single-Base

A codon that specifies the amino acid Ile undergoes a single-base substitution to become the amino acid Met. Which of the following describes the type of mutation that must have occurred?

A) a transition mutation at the first position of the codon
B) a transversion mutation at the first position of the codon
C) a transition mutation at the third position of the codon
D) a transversion mutation at the third position of the codon
E) a transition mutation or a transversion mutation at the third position of the codon