Billings method of contraception is based on -

Ans. is 'b' i.e., Change in cervical mucus Miscellaneous methods of contraceptionso These are (i) Abstinence, (ii) Coitus interruptus, (iii) Safe period (rhyth method), and (iv) Natural family planning methods.Abstinenceo There is complete abstinence from sexual intercourse. It is not used and can hardly be considered as a method of contraception to be advocated to the masses.Coitus interruptuso It is the oldest method of voluntary fertility control. The male withdraws before ejaculation, and thereby tries to prevent deposition of semen into vagina. Failure rate is very high 25%.Natural family planning methodso These areBasal body temperature (BBT) method : It is based on the principle that there is rise BBT at or just before ovulation.Cervical mucus method (Billings method or ovulation method) : It is based on the observation that at the time of ovulation cervical mucus becomes watery clear resembling raw egg white, smooth, slippery' and profuse.Symptothermic method : This method combines temperature, cervical mucus and safe period (calender method) methods.