Question

a codon consists of:
3 nitrogenous bases on trna
4 nitrogenous bases
2 rna strands
3 nitrogenous bases on mrna

Explanation:

A codon is a sequence of 3 nitrogenous bases that codes for an amino acid, and it is located on messenger RNA (mRNA). The complementary 3-base sequence on tRNA is called an anticodon, not a codon. The other options incorrectly describe the structure or location of a codon.

Answer:

3 nitrogenous bases on mRNA