This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
A codon consists of 
Select and explain. 
A. Two complementary base pairs, B. Three consecutive nucleotide units, C. An individual ribosome, D. Four individual nucleotides
B: Three consecutive nucleotide units
Answer: B: Three consecutive nucleotide units 
Explanation: A codon is a sequence of 3 nucleotides from 5' → 3' end corresponds to one amino acid.