Final answer:
The taxonomic domain that includes multicellular photosynthetic organisms such as plants and certain algae is Domain Eukarya, which encompasses Kingdom Plantae and some groups of green algae.
Step-by-step explanation:
The taxonomic domain that includes multicellular photosynthetic organisms such as plants and certain algae is Domain Eukarya. This domain is characterized by cells with nuclei and encompasses several kingdoms, including the animal, plant, fungus, and protist kingdoms. the Kingdom Plantae within this domain consists of multicellular, autotrophic organisms that utilize photosynthesis to create their own food, primarily glucose.
Additionally, it includes groups of green algae, such as Chlorophyta and Charaphyta, which also contain chlorophyll and engage in photosynthesis, even though not all green algae are multicellular.