A bacterium which has been genetically modified to control pollution is
A. Pseudomonas
B. Rhizobium
C. Nitrobacter
D. Nitrosomonas

Hint: Genetically modified bacteria were the first organisms to be modified in the laboratory, because of their basic genetics. These organisms are now utilized for a few purposes and are particularly important in producing a lot of unadulterated human proteins for use in medicine.

Step by step answer:Genetically modified bacteria are tailor-made bacteria. Pseudomonas is naturally a biocontrol agent which can be utilized for the cycle of bioremediation. They produce enzymes which are fit for degrading the organic waste. A portion of the strains of the Pseudomonas is genetically modified so it is utilized to control pollutants for a huge scope, for example, oil slicks that take place in the ocean. A portion of the strains from Pseudomonas is even transferred in E. coli to create the enzymes equipped for degrading organic compounds. This was done to increase the production of the enzymes.
Thus, the correct answer is 'Pseudomonas' option A
Nitrobacter is a genus comprising bar formed, gram-negative, and chemoautotrophic bacteria. Nitrobacter assumes an important function in the nitrogen cycle by oxidizing nitrite into nitrate in soil any marine systems. So, option c is incorrect
Nitrosomonas assume an important function in providing nitrogen to plants and limiting carbon dioxide fixation. They are found generally distributed in soil or water. So, option D is incorrect.
To communicate genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. In general, they are gram-negative, motile, non-sporulating bars. So, option B is incorrect.

Note: Aliphatic And Aromatic Hydrocarbons, Raw Petroleum, Nitroaromatic Compounds Are Effectively Debased by a wide range of Pseudomonas sp. Most of the strains contained a catabolic plasmid, which encodes the genes for hydrocarbon degradation. The biotransformation of this plasmid to different terrestrial and natural marine bacteria has been done, indicating the horizontal transfer of catabolic genes starting with one bacteria then onto the next, to create "superbugs" for bioremediation program in ecosystems.