The correct answer is H1.

- In the structure of chromatin, nucleosomes are the fundamental repeating units, consisting of DNA wrapped around a core of histone proteins. The nucleosome core particle is made up of an octamer containing two copies each of the four core histones: H2A, H2B, H3, and H4. Specifically, the DNA wraps approximately 1.65 turns around this histone octamer, which helps compact the DNA into a more condensed form.

- The histone H1, however, is not part of this core particle. Instead, it is known as the linker histone and binds to the DNA between nucleosomes (called linker DNA). Its role is to help stabilize the higher-order structure of chromatin by promoting the folding of nucleosomes into more compact fibers.

To summarize:
- H2A, H2B, H3, and H4: core histones that form the nucleosome core particle.
- H1: linker histone that is excluded from the nucleosome core particle and helps in chromatin compaction.

Reference: Molecular Biology of the Cell, 6th Edition, Alberts et al., Chapter 6 – The Structure and Function of Chromatin / p.290