Cyanobacteria are a group of photosynthetic bacteria that are capable of performing oxygenic photosynthesis. During this process, they use sunlight to convert carbon dioxide and water into organic compounds, while producing oxygen as a byproduct. This oxygen production is a key characteristic of oxygenic photosynthesis, and is what allows cyanobacteria to release oxygen into the atmosphere.

In addition to oxygenic photosynthesis, many species of cyanobacteria also have the ability to fix atmospheric nitrogen into a form that can be used by other organisms. This process is facilitated by an enzyme called nitrogenase, which converts nitrogen gas into ammonia, a compound that can be taken up by plants and other organisms. Cyanobacteria are the primary nitrogen fixers in many ecosystems, and they play a critical role in maintaining the balance of nutrients in many environments.

So, to summarize, cyanobacteria are oxygenic because they produce oxygen during photosynthesis, and they are capable of fixing nitrogen because they contain the enzyme nitrogenase. Option A, "Oxygenic with nitrogenase," is the correct answer.