The organisms without a cell wall and can live without oxygen are

• A. Thermoacidophiles
• B. Methanogens
• C. Archaebacteria
• D. Mycoplasma

The organisms that lack a cell wall and can survive without oxygen are known as Mycoplasma. These are a type of bacteria that are unique due to their flexible structure and ability to thrive in anaerobic environments.

Key Characteristics of Mycoplasma

• No Cell Wall: Mycoplasma do not have a rigid cell wall, which allows them to change shape.
• Anaerobic Survival: They can live in environments without oxygen, making them quite versatile.
• Small Size: Mycoplasma are among the smallest known bacteria, often requiring special techniques for observation.

Other Options Explained

While Thermoacidophiles and Methanogens are interesting organisms, they either have cell walls or are not classified as Mycoplasma. Archaebacteria is a broader category that includes various types of microorganisms, some of which may have cell walls.