The correct options are
A Can be used as an emergency birth control.
B Causes hormonal imbalance.
D Prevents fertilization between the sperm and egg.
Contraceptive pills act by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. These drugs commonly need to be taken orally as pills. However, since they change hormonal balances, they can cause side-effects too. STDs cannot be prevented by using contracepive pills.