**Core Concept**
Nucleosomes are the fundamental units of chromatin structure, formed by the wrapping of DNA around a core of histone proteins. This complex arrangement allows for the condensation and packaging of DNA within the nucleus, thereby regulating gene expression and facilitating DNA replication and repair.

**Why the Correct Answer is Right**
Nucleosomes are composed of a segment of DNA (approximately 147 base pairs) that is wrapped around a core of eight histone proteins (two copies each of histones H2A, H2B, H3, and H4). This interaction between DNA and histones is mediated by the positively charged amino-terminal tails of the histones, which bind to the negatively charged phosphate groups of the DNA backbone. This complex structure is stabilized by various protein-DNA interactions, including histone-DNA contacts and histone-histone interactions.

**Why Each Wrong Option is Incorrect**
**Option A:** DNA+RNA is incorrect because RNA is not a component of nucleosomes. While RNA is essential for various cellular processes, such as transcription and translation, it is not directly involved in the formation of nucleosomes.
**Option C:** RNA+Histones is incorrect because RNA is not a component of nucleosomes, as explained above. Additionally, histones are the primary proteins that interact with DNA in nucleosomes, not RNA.
**Option D:** DNA+RNA+Histones is incorrect because RNA is not a component of nucleosomes. As mentioned earlier, RNA plays a distinct role in cellular processes, separate from the formation and structure of nucleosomes.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that nucleosomes play a crucial role in regulating gene expression through epigenetic modifications, such as histone acetylation and methylation. These modifications can influence chromatin structure and accessibility, thereby affecting gene transcription and cellular behavior.

**✓ Correct Answer: B. DNA+Histones**