Final answer:
Histone H1 plays a crucial role in DNA compaction by linking adjacent nucleosomes, which helps to form the 30nm chromatin fibre and stabilize the chromosome's structure. Option c is correct.
Step-by-step explanation:
The role of histone H1 in compaction to the 30nm fibre is to link adjacent nucleosomes. This linking is a crucial step in the second level of DNA compaction, which involves coiling the nucleosomes and the linker DNA into a 30-nm chromatin fibre.
This coiling and the presence of histone H1 compact the chromosome to about 50 times shorter than its extended form. By doing so, H1 helps stabilize the higher-order structure of chromatin.