Final answer:
The surge in LH that occurs during the middle of the ovarian cycle triggers ovulation.
Step-by-step explanation:
The surge in LH that occurs during the middle of the ovarian cycle triggers ovulation. Ovulation is the process in which the mature follicle ruptures and releases its egg. This is stimulated by a sudden rise in the blood level of luteinizing hormone (LH) from the pituitary gland.