DNA condenses inside cells by compacting around

DNA condenses inside cells by compacting around histones. Histones are proteins that act as spools around which DNA is wrapped, forming a structure called a nucleosome. This compaction allows the long DNA molecule to fit inside the small nucleus of a cell. The DNA-histone complex further coils and folds to form higher-order structures, ultimately leading to the formation of chromosomes during cell division.

Option A, histone, is the correct answer. Histones play a crucial role in DNA packaging and organization. They have a positive charge due to the presence of many basic amino acids, such as lysine and arginine. This positive charge allows histones to interact with the negatively charged DNA molecule, facilitating its compaction.

Options B, C, and D are incorrect. Carbon is an element that is not directly involved in DNA condensation. RNA is a molecule that is structurally similar to DNA but does not play a significant role in DNA condensation. Nitrogenous bases are the building blocks of DNA, but they do not directly contribute to the compaction of DNA inside cells.

In summary, DNA condenses inside cells by compacting around histones. Therefore, the correct answer is A.