Which amongst the following scientists was successful in discovering that the genetic code is a “triplet”?

The correct option is B Marshall Nirenberg
$\begin{array}{cc}\text{Scientists}& \text{Discovery}\\ \text{Meselson and Stahl}\to & \text{Experimental proof for the semiconservative model of}\\ & \text{DNA replication. In this model, each}\\ & \text{strand of DNA serves as a template}\\ & \text{and produces a new}\\ & \text{complementary strand such that the}\\ & \text{daughter DNA contains one parental}\\ & \text{strand and one newly synthesised}\\ & \text{strand.}\\ \text{Marshall Nirenberg}\to & \text{Genetic code is triplet. He}\\ & \text{had deciphered the 64 codons and}\\ & \text{had established that genetic code is}\\ & \text{triplet.}\\ \text{Hershey and Chase}\to & \text{DNA is the genetic material}\\ \text{Morgan and Sturtevant}\to & \text{First genetic linkage map}\end{array}$