Azolla is a

Algae
Fungi
Bryophyta
Aqueous fern

Azolla is a genus of aquatic ferns that live in freshwater habitats. They are small, free-floating plants that can form dense mats on the surface of the water. Azolla is a nitrogen-fixing plant, which means that it can convert atmospheric nitrogen into ammonia, a form of nitrogen that plants can use. This makes azolla a valuable crop for farmers, as it can be used to fertilize crops and improve soil quality.

Algae are a diverse group of photosynthetic organisms that are not plants. They are typically single-celled, but some algae can form colonies or even multicellular organisms. Algae are found in a wide range of habitats, including freshwater, saltwater, and soil. They play an important role in the food chain and are a source of food for many animals.

Fungi are a diverse group of eukaryotic organisms that are not plants or animals. They are typically multicellular, but some fungi can be unicellular. Fungi are found in a wide range of habitats, including soil, water, and on living and dead organisms. They play an important role in the decomposition of organic matter and the cycling of nutrients.

Bryophyta are a group of non-vascular plants that include mosses, liverworts, and hornworts. They are typically small, simple plants that lack true roots, stems, and leaves. Bryophytes are found in a wide range of habitats, including moist forests, bogs, and even on rocks. They play an important role in the colonization of new habitats and the formation of soil.

The correct answer to the question “Azolla is a” is D. Aqueous fern.