NEET BIOLOGY

Detailed explanation-1: -Final answer: Mycoplasma is the smallest living cell, known without a definite cell wall, pathogenic to plants as well as animals, and can survive without oxygen.

Detailed explanation-2: -Mycoplasma is the smallest cell which does not possess cell wall as an outer covering but has cell membrane as an outer covering. As they do not have cell wall they do not get affected by the antibiotics and causes severe diseases to the plants and animals.

Detailed explanation-3: -The smallest living cells are Mycoplasmas. They lack a cell wall. Mycoplasma pneumoniae is a well established human pathogen. Mycoplasmas may be aerobes or facultative anerobes.

Detailed explanation-4: -Mycoplasma is the smallest living cell which lacks cell wall and can survive without oxygen. They are facultative anaerobes, so they can switch to anaerobic mode in the absence of oxygen except for M. pneumoniae, which is a strict aerobe.

Detailed explanation-5: -Bacteria have a prominent cell wall and thus, this is the smallest microorganism with a cell wall. Therefore, this is the correct option. Thus, the correct answer option is (D) Bacteria.