The correct answer is B. Blue green algae.
Heterocysts are specialized cells in cyanobacteria that are responsible for nitrogen fixation. Nitrogen fixation is the process by which atmospheric nitrogen is converted into ammonia, which can then be used by plants and other organisms. Heterocysts are able to fix nitrogen because they contain a specialized enzyme called nitrogenase. Nitrogenase is an essential enzyme for nitrogen fixation, but it is also very sensitive to oxygen. To protect nitrogenase from oxygen, heterocysts have a number of adaptations, including a thick cell wall and a reduced oxygen concentration.
Red brown algae, ferns, and mosses do not have heterocysts. Red brown algae are a type of algae that are found in marine environments. Ferns are a type of plant that are found in both terrestrial and aquatic environments. Mosses are a type of plant that are found in terrestrial environments.
Here is a brief explanation of each option:
- Red brown algae: Red brown algae are a type of algae that are found in marine environments. They do not have heterocysts.
- Blue green algae: Blue green algae are a type of bacteria that are found in both aquatic and terrestrial environments. They do have heterocysts.
- Ferns: Ferns are a type of plant that are found in both terrestrial and aquatic environments. They do not have heterocysts.
- Mosses: Mosses are a type of plant that are found in terrestrial environments. They do not have heterocysts.