Which of the following is not a unicellular organism? A. Amoeba B. Yak C. Yeast D. Rhizobium

Cellular organisms are classified into two groups: prokaryotes and eukaryotes. The genetic material, deoxyribonucleic acid (DNA) is organized into chromosomes. The chromosomes in a eukaryotic cell are surrounded by a nuclear membrane, forming a true nucleus. Complete answer: A unicellular organism, also known as a single-celled organism, is an organism made up of a single cell, as opposed to a multicellular organism, which is made up of multiple cells. Unicellular organisms are classified into two types: prokaryotic organisms and eukaryotic organisms. Option (A) Amoeba: Amoeba is referred to as a unicellular organism because it only has one cell. A single-cell organism is referred to as a unicellular organism. This means that all life processes, including reproduction, feeding, digestion, and excretion, take place in a single cell. Option (B) Yak: The domestic yak is a long-haired domesticated cattle that can be found throughout the Indian subcontinent's Himalayan region, the Tibetan Plateau, Northern Myanmar, Yunnan, Sichuan, and as far north as Mongolia and Siberia. It is a descendant of the wild yak. Yaks are a type of multicellular organism. Option (C) Yeast: Yeasts are eukaryotic, unicellular microorganisms that belong to the fungus kingdom. The first yeast appeared hundreds of millions of years ago, and at least 1,500 species are now known. They are estimated to account for 1% of all described fungal species. Option (D) Rhizobium: Rhizobium is a bacterial genus that is linked to the formation of root nodules on plants. It is a unicellular bacteria. These bacteria coexist with legumes in a symbiotic relationship. They absorb nitrogen from the atmosphere and pass it on to the plant, allowing it to grow in nitrogen-deficient soil. Multicellular organisms are made up of multiple cells. Yaks, for example, are multicellular organisms. Yak is not a unicellular organism in this context. Thus, the answer is option (B), Yak. Note: Many unicellular organisms live in bodies of water and must move around in search of food. The majority of the time, they must obtain nutrients by eating other organisms. Photosynthesis allows plant-like protists and some bacteria to produce their food.