The correct option is D Enterococcus
Enterococci are Gram-positive cocci that occur in pairs or short chains. They give a positive result in the Gram staining test. They take up the crystal violet stain and appear purple under a microscope. The thick peptidoglycan layer in the bacterial wall retains the stain even after it is washed away from the rest of the cell portion during the decolourization stage of the test. Thus, the correct answer is option D.