Final answer:
The X-inactivation center (Xic) is the major control region for X inactivation in mammals.
Step-by-step explanation:
The major control center of X inactivation in mammals is A) Xic, which stands for X-inactivation center. The X-inactivation center is a region on the X chromosome that plays a crucial role in the process where one of the two X chromosomes in female mammals becomes inactivated. This process is vital for dosage compensation because it ensures that females, who have two X chromosomes, do not produce double the amount of X chromosome gene products compared to males, who have only one X chromosome.