This organism is multicellular and has a cell wall but no chloroplasts. The organism gets the energy it needs by decomposing organic matter. To what kingdom does this organism belong?

This organism belongs to Kingdom Fungi.

Explanation:

Fungi are heterotrophic, spore bearing Eukaryotes. Most of the fungi are multicellular. Their cells have a cell wall mainly composed of Glucagon and chitin. These are saprotrophic and lack a chloroplasts. They store food as glycogen which is similar to storage product in animals. The Kingdom fungi is divided into four major division on the basis of sexual reproduction; chydridomycota, zygomycota, ascomycota and basidiomycota. Many fungi show no sexual stage and are grouped as imperfect fungi or deuteromycetes. The study of fungi is called Mycology.