Histones are proteins that act as spools so the DNA can create structural units around them (nucleosomes). While the DNA is negatively charged, the histones are positively charged, which is important so them both can associate with each other. As the histones are present in the cell nucleus, they can't be found in prokaryotic cells as those has no nuclei. So, only eukaryotic cells have histones.
Therefore, the correct answer is b) Positively charged proteins that help to organise DNA in eukaryotic cells.
