Answer is A. Archaebacteria
Archaebacteria are a type of single-cell organism. They are a group of most primitive prokaryotes which are believed to have evolved immediately after the evolution of the first life. Thermoacidophiles are the archaebacteria which can tolerate high temperature as well as high acidity. They often live in hot sulfur springs where the temperature may be as high as 80°C and pH as low as 2. Examples are Thermoplasma, Thermoproteus.