Read the following statements.
a) The negatively charged DNA is wrapped around positively charged histone octamer to form a structure called a nucleosome.
b) A typical nucleosome contains approximately 200 bps of DNA helix.
c) The nucleosomes in chromatin are seen as beads on a string structure when viewed under an electron microscope.
d) Histones are positively charged basic proteins.
Choose correct statements.

a) The negatively charged DNA is wrapped around positively charged histone octamer to form a structure called nucleosome. This statement accurately describes the formation of nucleosomes. DNA, which is negatively charged due to its phosphate backbone, wraps around a positively charged histone octamer to create the nucleosome, which is the fundamental unit of chromatin structure.

b) A typical nucleosome contains 200 Bp of DNA helix. A typical nucleosome contains approximately 200 base pairs of DNA wrapped around the histone octamer. 

c) The nucleosomes in chromatin are seen as beads on a string structure when viewed under an electron microscope. This statement is accurate. Under an electron microscope, chromatin often appears as a "beads on a string" structure, with nucleosomes (the "beads") connected by stretches of linker DNA (the "string"). This arrangement reflects the packaging of DNA in eukaryotic cells.

d) Histones are positively charged basic proteins. This statement is correct. Histones are a family of basic proteins rich in positively charged amino acids such as lysine and arginine. Their positive charge allows them to interact with the negatively charged phosphate groups of DNA, facilitating the binding and compaction of DNA into nucleosomes and chromatin.
So, the correct statements are (a), (b), (c), and (d).