The correct answer is B - nucleoid.
The nucleoid is a region in a prokaryotic cell that houses the main DNA material of the cell.
In contrast to eukaryotic cells with a nucleus, prokaryote have a nucleoid where the genetic material can be found. The nucleoid is different from the nucleus in eukaryotes in that the genetic material is not enclosed in a membrane to separate it from the cytoplasm.
The nucleoid usually contains only a single chromosome which has the cell DNA.