Question

A teacher says she has identified an organism with these characteristics: eukaryotic, multicellular, autotrophic, and a cell wall made of cellulose. Which kingdom is the teacher describing?

Answer 1

Let's break down each of the words to find out what they mean.
Eukaryotic: This basically means that the organism in question has a nucleus and other membrane-bound organelles. This rules out bacteria and archaea.
Multicellular: The organism must be made up of one or more cells, so that rules out protists.   
Autotrophic: This means that the organism can make energy from inorganic substances via a light source or chemical energy. Finally, this rules out animals and fungi.
Cell wall: This also proves that the organism is a plant. Plants are the only organisms that have a cell wall made of cellulose; fungi have one, but they are made of chitin and glucans.

So, your answer is that the kingdom of the organism of a plant. 

Answer 2

I'm pretty sure that what the question is describing is a "plant cell".