The initial idea of triplet nature of codon was proposed by:

George Gamow

The correct answer is Option (1) → George Gamow

It was George Gamow, a physicist, who argued that since there are only 4 bases and if they have to code for 20 amino acids, the code should constitute a combination of bases. He suggested that in order to code for all the 20 amino acids, the code should be made up of three nucleotides. This was a very bold proposition, because a permutation combination of 4³ (4 × 4 × 4) would generate 64 codons; generating many more codons than required.