Answer:
Autotroph: an organism capable of making its own food from carbon dioxide.
Heterotroph: an organism that cannot make its own food and thus has to eat either autotrophs or other heterotrophs for energy.
Decomposer: an organism that breaks down dead or decaying organisms; such decomposers are bacteria and fungi.
Unicellular: an organism that consists of one cell, such as bacteria. Some unicellular organisms have a nucleus and are called eukaryotes, while some have no nucleus, such as bacteria, which are called prokaryotes.
Multicellular: an organism that consists of many cells, such as you and I, and many other animals.
Hope this helps :)