A scientist is trying to determine which clade an organism best fits into based on its characteristics. He has determined that the organism must belong to either the clade of bacteria or fungi. Which of the following characteristics would best indicate that the organism is a bacterium?
A.
The organism is heterotrophic and cannot make its own food.
B.
The organism's cells each contain a membrane-bound nucleus.
C.
The organism can move around its environment using a flagellum.
D.
The organism is made up of more than one cell.

Although most of the bacteria are Heterotrophs but a variety of species of them are Autotrophs making their own food. Hence option a) is incorrect.
Bacteria belong to prokaryotes which means they do not have a well defined membrane bound nucleus. hence option b) is also incorrect.
Most of the bacteria can move through flagella only a few species do not have flagella. Hence this option matches the most.
Bacteria are unicellular organism and none of the species of bacteria is multicellular. Hence option d) is incorrect.

Resut: Option C) matches the most for defining bacteria.