Final answer:
Combination oral contraception used as emergency contraception works through multiple mechanisms of action including preventing ovulation, changing the cervical mucus, and altering the uterine lining.
Step-by-step explanation:
Combination oral contraception, specifically when used as emergency contraception, works through multiple mechanisms of action. The pill contains both estrogen and progestin hormones that prevent the ovaries from releasing an egg. It also changes the cervical mucus and uterine lining, making it difficult for sperm to reach the egg and for a fertilized egg to implant in the uterus. These mechanisms together make combination oral contraception an effective method of emergency contraception.