Final answer:
Combined hormone methods prevent sperm from joining an egg by thickening the cervical mucus, with the intended site of interception being the Fallopian tube.
Step-by-step explanation:
Combined hormone methods use a blend of hormones, specifically synthetic progesterone and sometimes estrogen, to suppress ovulation and thicken the cervical mucus, making it more difficult for sperm to reach an egg. These methods include oral contraceptives, the vaginal ring, and other forms of hormonal contraception like patches and injections. The purpose of the cervical mucus thickening is to prevent sperm from joining the egg, which typically takes place within the Fallopian tube. Therefore, the correct answer to the student's question is C) Fallopian tube.