You collect a protist from a rotting log and grow it in a petri dish containing E. coli, which it engulfs. For a while the protists multiply as single cells. Then the E. coli run short, and the protists aggregate to form a clump, which rises up to become a stalked structure with a globular head. What kind of protist have you got?

A) an actinomycete

B) a plasmodial slime mold

C) a cellular slime mold

D) a free-living amoeba

E) a water mold