Which of the following processes occurs without the use of oxygen?

Fermentation is a metabolic process that occurs in the absence of oxygen, allowing organisms to convert carbohydrates into acids, gases, or alcohol. This anaerobic process enables cells to generate energy when oxygen is unavailable. For example, in yeast cells, fermentation produces ethanol and carbon dioxide from glucose, while in muscle cells, it can lead to the production of lactic acid during intense activity when oxygen levels are low.

The other processes mentioned require oxygen. Oxygen respiration, which is often referred to as aerobic respiration, is a process where glucose is broken down in the presence of oxygen to produce carbon dioxide, water, and energy in the form of ATP. Photosynthesis, occurring in plants, algae, and some bacteria, also requires light energy and carbon dioxide to produce glucose and oxygen, thus relying on the presence of oxygen in the atmosphere. Aerobic respiration, much like oxygen respiration, requires oxygen to efficiently generate energy from food sources.

Understanding fermentation as an anaerobic process is key to recognizing how organisms adapt to different environments concerning oxygen availability.