The correct answer is D. Chromatids.
A chromosome is a long, thin structure found in the nucleus of most cells. It is made up of DNA and protein. Chromosomes are found in pairs, and each pair contains one chromosome from the mother and one chromosome from the father.
Chromatids are the two identical copies of a chromosome that are joined together at the centromere. During cell division, the chromatids separate and become individual chromosomes.
Genes are the basic units of heredity. They are located on chromosomes and are responsible for determining an organism’s physical characteristics.
Nuclei are the control centers of cells. They contain the chromosomes, which are responsible for storing and controlling the cell’s genetic information.
Bases are the building blocks of DNA. They are arranged in pairs, and the order of the pairs determines the genetic code.