What is the function of insulator sequences?

-mark intron/exon boundaries

-separate dna-binding and activation domains

-prevent unwanted enhancer/promoter interactions

-increase the size of the eukaryotic genome

-keep nucleosomes properly spaced

Option C,

prevent unwanted enhancer/promoter interactions

Explanation:

An insulator sequence consists of several binding sites in clusters that corresponds to specific DNA-binding proteins and leads to specific intra- and inter-chromosomal interactions. Insulators acts as a blocker or  barrier in all the cases as its main role is to prevent unwanted interactions between enhancer or promoter.

These are class of  DNA sequence elements that protect genes from taking inappropriate signals coming from surrounding environment thereby protecting  gene expression from its surroundings.

Hence, option C is correct