What does a female human possess in terms of sex chromosomes?

A female human possesses two X chromosomes as a defining characteristic of their sex chromosome composition. In humans, sex chromosomes are responsible for determining an individual's sex; females have two X chromosomes (XX), while males typically have one X and one Y chromosome (XY).

The presence of two X chromosomes allows for a range of genetic expressions that can influence various traits and biological functions. For instance, if one X chromosome carries a genetic mutation, the second X chromosome can sometimes mask the effects of that mutation due to a phenomenon known as X-inactivation or because it may carry the normal allele for that gene. This dual nature of X chromosomes in females is significant for understanding genetics, inheritance patterns, and conditions linked to sex chromosomes.

In contrast, the other choices present configurations that do not accurately represent the female sex chromosome structure: having a Y chromosome would indicate a male presence, receiving only one chromosome is an incomplete description, and having two Y chromosomes is not viable in humans. Thus, the possession of two X chromosomes is the sole option that accurately characterizes female human genetics.