Based on the characteristics you provided — multicellular, makes its own food, and is unable to move around — the organism Michelle is studying can most likely be classified into Kingdom A. Plantae.
Plants are multicellular, perform photosynthesis (make their own food), and are typically sessile (unable to move). The other options do not fit the given characteristics. Archaebacteria are unicellular, Animalia includes mobile organisms, and fungi are primarily decomposers and do not perform photosynthesis.