Assume that there are 6 types of nitrogen bases available and 40 types of amino acid are available for protein synthesis, then in genetic code each codon made up by minimum how many nitrogen codon made up by minimum how many nitrogen bases?

The correct option is A 3
The genetic code consists of 64 triplets of nucleotides. These triplets are called as codons. With three exceptions, each codon encodes for one of the 20 amino acids used in the synthesis of proteins. That produces some redundancy in the code. Most of the amino acids being encoded by more than one codon. The genetic code can be expressed as either RNA codons or DNA codons. RNA codons occur in messenger RNA (mRNA) and are the codons that are actually "read" during the synthesis of polypeptides (the process called translation). But each mRNA molecule acquires its sequence of nucleotides by transcription from the corresponding gene. Because DNA sequencing has become so rapid and because most genes are now being discovered at the level of DNA before they are discovered as mRNA or as a protein product, it is extremely useful to have a table of codons expressed as DNA. So here are both. So, in genetic code each codon is made of 3 bases. Thus, option A is correct and other options are wrong.