Core DNA wrapped around octamer core is base pair long.

146 base pair long

Explanation:

Nucleosome is a unit of DNA packaging in eukaryotic cells. It has segments of deoxyribonucleic acid(DNA) that is wrapped around eight histone protein in its structure. The DNA has 146 base pairs approximately of DNA that is wounded in 1.67 left-handed super helical turns around a histone octamer. It consist of 2 copies each of the core histones H2A, H2B, H3, and H4.

This Core particles are linked together by stretches of linker DNA, which can be up to about 80 bp long.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."