In the early 1900s a scientist hypothesized a link between dna and the production of proteins in the cytoplasm. however, the fact that dna could not be found outside the nucleus led scientists to believe that another substance was also involved in the synthesis of protein in the cytoplasm. in the 1940s scientists performed an experiment that ultimately identified the site of protein synthesis. they also identified the molecule responsible for transporting information form the nucleus to the site of protein synthesis. what was this newly identified molecule? a) a gene b) mrna c) atp d) thymine

Let us go over the definitions and the functions of each term:
a) Gene is a bit vague but in general it means a part of DNA that encodes one protein. Genes are the building blocks of our genomes but not the answer to this question.
b)mRNA. This is correct. The name itself means messengerRNA and its role is to copy the genetic information in the nucleus and bring it outside to be translated into protein.
c) ATP is an important molecule in our metabolism; energy is stored in this molecule and then used. It has no relationship to the mechanisms concerning DNA.
d) Thymine is one of the 4 nucleotide bases that are found in DNA, the other three being guanine, cytosine and adenine. They are essential components of a nucleotide (building blocks of DNA and RNA) but again, they do not transfer information out of the nucleus.