Consider the following statements : 1. Some microorganisms can grow in environments with temperature above the boiling point of water. 2. Some microorganisms can grow in environments with temperature below the freezing point of water. 3. Some microorganisms can grow in highly acidic environment with a pH below 3. How many of the above statements are correct?

Answer: C. All three statements about extremophilic microorganisms are correct. (1) Microorganisms growing above the boiling point: CORRECT. Hyperthermophiles (mostly archaea like Pyrolobus fumarii and Methanopyrus kandleri) thrive in deep-sea hydrothermal vents at temperatures above 100°C (some up to 122°C). They are studied for biotech applications including PCR (Taq polymerase). (2) Microorganisms growing below freezing: CORRECT. Psychrophiles such as bacteria from Antarctic sea ice and Greenland glaciers grow at temperatures down to about minus 20°C in liquid water trapped within ice channels. (3) Microorganisms in pH below 3: CORRECT. Acidophiles like Acidithiobacillus ferrooxidans and Picrophilus torridus thrive in highly acidic environments (pH 0-3) such as acid mine drainage, sulfuric hot springs. Some can even survive in pH near 0. Source: NCERT Class 12 Biology / standard microbiology references on extremophiles.