Final answer:
The true statement about sex chromosomes is that they carry genes not solely related to sex or gender. They determine sex in mammals by XX being female and XY being male, but can also influence traits unrelated to sexual development.
Step-by-step explanation:
The statement about sex chromosomes that is true is (c) Sex chromosomes carry some genes that may have nothing to do with sex or gender. While it is true that sex chromosomes, which consist of one X and one Y in males (XY) and two Xs in females (XX), are a significant factor in determining biological sex, they also contain genes that are not related to sexual development or characteristics.
For example, the X chromosome contains genes that are implicated in various other biological processes and disorders which are not related to gender. Additionally, while the sex is determined genetically in mammals by the presence of XX in females and XY in males, factors such as temperature can influence sex determination in other species.