Which of the following exemplifies a chemoautotroph ?

Nitrosomonas is an example of a chemoautotroph. Chemoautotrophs are a type of autotrophic organisms that obtain energy by oxidizing inorganic substances, and they use this energy to synthesize organic compounds from carbon dioxide. In the case of Nitrosomonas, it is a chemoautotrophic bacterium that plays a crucial role in the nitrogen cycle by oxidizing ammonia (NH₃) to nitrite (NO₂^-). This process, known as nitrification, releases energy that Nitrosomonas uses to support its growth and metabolism, and it also contributes to nitrogen cycling in ecosystems.