At what temperature threshold do extreme thermophiles begin to thrive?

Extreme thermophiles are a category of microorganisms that thrive at very high temperatures, often found in environments such as hot springs and hydrothermal vents. These organisms typically flourish at temperatures above 70°C, with many species being optimally active at temperatures ranging from 80°C to even 122°C. The temperature of 70°C is the threshold at which these organisms start to show significantly enhanced metabolic activity and growth, allowing them to outcompete other forms of life in extreme heat conditions.

At lower temperatures, such as those presented in the other options, microbial life is generally less adapted to cope with the extreme conditions associated with high temperatures. Therefore, the choice of 70°C as the beginning of optimal growth for extreme thermophiles reflects their unique adaptations to thrive in such environments.