The correct option is D both a and b
Plasmids are the small circular DNA outside the genomic DNA and found in prokaryotes like many bacteria. The plasmid DNA confers certain unique characters to bacteria like resistance to antibiotics and bacterial transformation (the ability to transform a non-pathogenic form to a pathogenic form).
The infoldings of cell membrane are called mesosomes. They are the characteristic of prokaryotes and are thought to increase the surface area of the cell, aiding the cell in cellular respiration.