There are 64 codons in the genetic code dictionary, because
A. There are 64 types of tRNAs found in the cell.
B. There are 44 meaningless and 20 codons for amino acids.
C. Genetic code is a triplet.
D. There are 64 amino acids to be coded.

Hint: Amino acids are joined to form polypeptide during translation because tRNAs are able to read the genetic code from the mRNA.
A combination of three bases constitutes each genetic code.

Complete answer: The process of protein synthesis is called translation.
1. As we know, mRNA contains many bases.
2. Three of such bases make up a codon that codes for a specific amino acid.
3. There are 64 such codons. In the translation process, those ‘codes’ of nitrogen bases are ‘translated’ or decoded into amino acids that make a polypeptide.
4. We know that there are four nitrogen bases in our DNA structure:
Adenine (A), Guanine (G), Thymine (T), and Cytosine (C).
5. Three bases constitute a triplet codon.
Each codon signals for an amino acid out of the 20 amino acids.
6. Hence there are 64 codons.

So, the correct option is C. Genetic code is triplet.

Note: Usually one codon codes for a single amino acid but exceptionally, more than one codon may code for the same amino acid e.g. GAA and GAG both code for glutamic acid. This property is called redundancy or degeneracy.