Final answer:
The most appropriate selection media for mutagenizing a bacterium to create a mutation in the his operon using the Tn10 transposon is minimal media, as it selects for mutants unable to synthesize the amino acid histidine.
Step-by-step explanation:
If the Tn10 transposon is used to mutagenize a bacterium for the purpose of creating a mutation in the his operon, the most appropriate selection media would be minimal media. This is because the his operon is responsible for the synthesis of histidine, an essential amino acid. If a mutation occurs in this operon, the bacterium will not be able to synthesize histidine and will only grow on a medium that contains histidine or in a minimal medium if the bacterium has no mutation and is able to synthesize it. Therefore, using minimal media allows for the selection of mutants that cannot synthesize histidine due to the disruption caused by the transposon. Other media types, like MacConkey agar, blood agar, and Lysogeny Broth, do not facilitate the selection based on an organism's ability to synthesize amino acids and hence are not appropriate in this case.