Ans. (A). cell type.
All organisms are classified into three kingdoms on the basis of their cell type, which include Monera, Protista, Fungi, Animalia, and Plantae.
Monera includes single-celled, prokaryotic organisms, such as bacteria and archaea. Cells of these organisms lack true nucleus and membrane bound organelles.
Protista include mostly single-celled eukaryotic organisms, such as amoeba and euglena. Eukaryotic cells have true nucleus and other membrane bound organelles.
Fungi includes fungus and other related organisms), such as yeast and mushroom. They have eukaryotic cells, surrounded by cell wall, like plant cells but they lack chloroplasts.
Animalia includes multicellular, eukaryotic organisms such as birds, fishes, insects, and humans. Animals also have cells with membrane bound organelles, but they lack cell wall.
Plantae include all the green plants, such as angiosperms, mosses, and ferns. Cells of these organisms are surrounded by a cell wall and have chloroplasts to perform photosynthesis.
So, the first characteristic that should be used to classify the organisms is to study their cell type. Thus, the correct answer is option (A).
