Which of the following do prokaryotes not contain?

a. DNA

b. a cell membrane

c. a nucleus

d. molecules floating inside

It has no definite nucleus but a region containing chromosome called nucleoid.

I think the correct answer from the choices listed above is option C. Prokaryotes do not contain a nucleus. These type of cells are unicellular and they lack organelles unlike eukaryotic cells. And one difference of this cell is that it has no nucleus only a nucleoid.