Final answer:
A rise in basal body temperature indicates ovulation.
Step-by-step explanation:
The rise in basal body temperature indicates d) Ovulation.
Basal body temperature is the lowest body temperature when the body is at rest, usually during sleep. It typically rises slightly after ovulation occurs and stays high until the start of the next menstrual period. This temperature rise is due to the increase in progesterone levels after ovulation. Therefore, a rise in basal body temperature indicates that ovulation has occurred and the woman may be fertile.