The correct answer is 4 major groups. Microorganisms are classified into different groups based on their characteristics and properties. These major groups are:

1. Bacteria: Bacteria are single-celled organisms that lack a nucleus and membrane-bound organelles. They are diverse and can be found in various environments, including soil, water, and even inside the human body.

2. Archaea: Archaea are also single-celled organisms that are similar to bacteria in terms of their simplicity, but they have distinct biochemical and genetic characteristics that differentiate them. They are often found in extreme environments such as hot springs and deep-sea hydrothermal vents.

3. Fungi: Fungi are a group of eukaryotic organisms that include molds, yeasts, and mushrooms. They are characterized by the presence of a cell wall and the ability to obtain nutrients through absorption. Fungi play important roles in decomposition and nutrient cycling in ecosystems.

4. Protists: Protists are eukaryotic microorganisms that do not fit into the categories of bacteria, archaea, or fungi. They are a highly diverse group that includes organisms such as amoebas, algae, and protozoa. Protists can be found in various environments and have a wide range of ecological roles