What type of chromosome is specifically involved in determining the sex of an organism?

The correct choice identifies sex chromosomes as the key elements involved in determining the sex of an organism. In many species, including humans, sex chromosomes play a critical role in the biological and genetic determination of sex. Humans have two sex chromosomes: X and Y. Females typically have two X chromosomes (XX), while males usually have one X and one Y chromosome (XY). The presence or absence of specific sex chromosomes leads to the development of male or female traits.

In contrast, autosomes, which are non-sex chromosomes, are involved in determining other hereditary traits but not in defining an organism's sex. The centromere is a region on a chromosome important for cell division, and while somatic chromosomes refer to the non-reproductive body cells, they do not specifically influence the determination of sex. Therefore, sex chromosomes are essential for sex determination in organisms, making this choice the most accurate answer.