Assertion : Periodic abstinence is a natural method where couples abstain from coitus Reason :Coitus from day 5-10 should be avoided because this is the time of ovulation.

Step-by-step solution

Periodic abstinence is a natural method of birth control in which the couples avoid or abstain from coitus (copulation or intercourse) from day 10 to 17 of the menstrual cycle because ovulation can occur during this period. The chances of fertilization are very high during this period, therefore, it is called the fertile period.