Final answer:
The kingdom that includes both unicellular and multicellular organisms is the protists. This diverse group houses eukaryotic organisms which do not fall under plant, animal, or fungal kingdoms, ranging from microalgae to giant seaweeds.
Step-by-step explanation:
Kingdoms Including Unicellular and Multicellular Organisms
The correct answer to which kingdom includes both unicellular and multicellular organisms is protists (option b). The protists kingdom is an immensely diverse group that consists of unicellular organisms such as microalgae and plankton, as well as multicellular organisms like giant kelps and seaweeds. This kingdom serves as a catchall category for eukaryotic organisms that do not fit easily into other kingdoms such as plants, animals, or fungi.
When looking at prokaryotic cells, we find them in domains and not kingdoms. These domains include the Bacteria and Archaea, both consisting of organisms that are unicellular and lack nuclei, making them prokaryotes. They are different from eukaryotic cells, which are characteristic of protists, plants, animals, and fungi, all of which have cells with nuclei and may be uni- or multicellular.