ANS:D - all the above.

• All the above.

1. Anaerobic bacteria flourish in the absence of oxygen: Anaerobic bacteria are organisms that can thrive and carry out metabolic processes in environments where oxygen is absent or in low concentrations. These bacteria obtain energy through anaerobic respiration or fermentation, converting organic compounds into simpler forms without the need for oxygen.
2. Aerobic bacteria flourish in the presence of oxygen: Aerobic bacteria are organisms that require oxygen to carry out their metabolic processes. They use oxygen as a terminal electron acceptor in cellular respiration, allowing them to generate energy efficiently from organic compounds. Aerobic bacteria are common in environments where oxygen is available, such as soil, water, and the human body.
3. Facultative bacteria flourish with or without oxygen: Facultative bacteria are versatile organisms that can adapt to different environmental conditions. They are capable of thriving in the presence or absence of oxygen by switching between aerobic and anaerobic metabolism depending on the availability of oxygen. This flexibility allows facultative bacteria to survive in diverse habitats and play important roles in various biological processes, including wastewater treatment, decomposition, and fermentation.