The correct option is D Both a and b
Birth control is any method used to prevent pregnancy. There are many different methods of birth control like natural, barrier, chemical, etc.
Abstaining from coitus between 10th-17th day of menstrual cycle which is also called periodic abstinence can prevent pregnancy as ovulation occurs during this period.
Withdrawing the penis from the female reproductive tract before ejaculation prevents entry of sperms in the female reproductive tract, hence avoids fertilisation. This method is called withdrawal or coitus interruptus.
Abortion has to be prescribed by a medical practitioner legally after the consent of the couple.