The correct answer is isobutanol.
Genetic engineering is the branch in which a little manipulation in the DNA of the organism can help in production of the desired product. The cyanobacteria belongs to the phylum of bacteria that performs photosynthesis.
The synthesis of isobutanol cab be done by genetically modified cyanobacteria as these modified cyanobacteria produce biofuels, such as isobutanol with the help of solar energy and carbon dioxide. They grow faster as compared to plants and absorb sunlight more efficiently so they can replenish more isobutanol.