Answer:
d. a bacterium with human gene for producing insulin
Explanation:
Transgenic organisms are the organisms in which the foreign DNA is introduced by using the molecular techniques for obtaining a particular result. This foreign DNA can be introduced using a vector called plasmid vector.
One of the examples of transgenic organisms is E.coli with the human gene for producing insulin. So for producing artificial insulin, the gene which produces insulin peptide is ligated in a plasmid vector and then this plasmid is introduced in the bacterium where this plasmid replicates and produces insulin. So the correct answer is d.