Biology question: Chromosome Structure

When you want to work with string without it becoming a tangled mess, you coil it up into a neat little bundle or ball. in a cell, these bundles of DNA are called _______ a.) Chromosomes b.) sister chromatids c.) histones . Proteins called ______ a.) histones b.) centromeres c.) nucleosomes help the DNA coil properly.
_______ a.) sister chromatids b.) histones c.) nucleosomes form when the DNA in a chromosome is copied exactly to form an identical strand of DNA.

If you could explain that would be helpful thank you so much.

When you want to work with string without it becoming a tangled mess, you coil it up into a neat little bundle or ball. in a cell, these bundles of DNA are called _a.) Chromosomes. Proteins called _a.) histones help the DNA coil properly.
a.) sister chromatids form when the DNA in a chromosome is copied exactly to form an identical strand of DNA.