How does copper-T prevent pregnancy?

Which method of contraception prevents fertilised egg from being implanted in the uterus?

What substances are contained (i) in oral pills, and (ii) in vaginal pills, used as contraceptives? How do they work?

Name the disease caused by HIV.

What is the name of surgical method of birth control (or preventing pregnancy) which is carried out (i) in men, and (ii) in women ?